@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-Bold.eot');
    src: url('fonts/Ubuntu-Bold.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-Bold.woff2') format('woff2'),
        url('fonts/Ubuntu-Bold.woff') format('woff'),
        url('fonts/Ubuntu-Bold.ttf') format('truetype');
    font-weight: bold;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-BoldItalic.eot');
    src: url('fonts/Ubuntu-BoldItalic.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-BoldItalic.woff2') format('woff2'),
        url('fonts/Ubuntu-BoldItalic.woff') format('woff'),
        url('fonts/Ubuntu-BoldItalic.ttf') format('truetype');
    font-weight: bold;
    font-style: italic;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-Italic.eot');
    src: url('fonts/Ubuntu-Italic.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-Italic.woff2') format('woff2'),
        url('fonts/Ubuntu-Italic.woff') format('woff'),
        url('fonts/Ubuntu-Italic.ttf') format('truetype');
    font-weight: normal;
    font-style: italic;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-LightItalic.eot');
    src: url('fonts/Ubuntu-LightItalic.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-LightItalic.woff2') format('woff2'),
        url('fonts/Ubuntu-LightItalic.woff') format('woff'),
        url('fonts/Ubuntu-LightItalic.ttf') format('truetype');
    font-weight: 300;
    font-style: italic;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-MediumItalic.eot');
    src: url('fonts/Ubuntu-MediumItalic.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-MediumItalic.woff2') format('woff2'),
        url('fonts/Ubuntu-MediumItalic.woff') format('woff'),
        url('fonts/Ubuntu-MediumItalic.ttf') format('truetype');
    font-weight: 500;
    font-style: italic;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-Medium.eot');
    src: url('fonts/Ubuntu-Medium.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-Medium.woff2') format('woff2'),
        url('fonts/Ubuntu-Medium.woff') format('woff'),
        url('fonts/Ubuntu-Medium.ttf') format('truetype');
    font-weight: 500;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-Light.eot');
    src: url('fonts/Ubuntu-Light.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-Light.woff2') format('woff2'),
        url('fonts/Ubuntu-Light.woff') format('woff'),
        url('fonts/Ubuntu-Light.ttf') format('truetype');
    font-weight: 300;
    font-style: normal;
    font-display: swap;
}

@font-face {
    font-family: 'Ubuntu';
    src: url('fonts/Ubuntu-Regular.eot');
    src: url('fonts/Ubuntu-Regular.eot?#iefix') format('embedded-opentype'),
        url('fonts/Ubuntu-Regular.woff2') format('woff2'),
        url('fonts/Ubuntu-Regular.woff') format('woff'),
        url('fonts/Ubuntu-Regular.ttf') format('truetype');
    font-weight: normal;
    font-style: normal;
    font-display: swap;
}

:root {
    --bg-main: #ffffff;
    --bg-canvas: #fafafa;
    --grid-color: rgba(30, 30, 30, 0.07);
    --text-color: #1e1e1e;
    --border-color: #1e1e1e;
    --muted-text: #5c5f63;
    --panel-bg: rgba(255, 255, 255, 0.95);
    --shadow: 0px 8px 30px rgba(0, 0, 0, 0.08);
    --toolbar-border: 2px solid #1e1e1e;
}

[data-theme="dark"] {
    --bg-main: #121212;
    --bg-canvas: #1a1a1a;
    --grid-color: rgba(255, 255, 255, 0.05);
    --text-color: #f5f5f5;
    --border-color: #f5f5f5;
    --muted-text: #c7c7c7;
    --panel-bg: rgba(30, 30, 30, 0.95);
    --shadow: 0px 8px 30px rgba(0, 0, 0, 0.4);
    --toolbar-border: 2px solid #f5f5f5;
}

body {
    font-family: 'Plus Jakarta Sans', sans-serif;
    background-color: var(--bg-main);
    color: var(--text-color);
    height: 100vh;
    overflow: hidden;
    transition: background 0.3s, color 0.3s;
}

.home-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
}

.home-page .excalidraw-floating-toolbar,
.home-page .floating-popover-panel {
    position: absolute;
}

.excalidraw-floating-toolbar {
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    width: max-content;
    max-width: calc(100vw - 32px);
    box-sizing: border-box;
    background: var(--panel-bg);
    border: var(--toolbar-border);
    border-radius: 12px;
    box-shadow: var(--shadow);
    padding: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    z-index: 1050;
    backdrop-filter: blur(10px);
}

.toolbar-divider {
    width: 2px;
    height: 28px;
    background-color: var(--text-color);
    opacity: 0.2;
}

.toolbar-trigger-btn {
    background: transparent;
    border: 2px solid transparent;
    color: var(--text-color);
    font-weight: 700;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.2s ease;
}

.toolbar-trigger-btn:hover, .toolbar-trigger-btn.active {
    background: var(--text-color);
    color: var(--bg-main);
}

.floating-popover-panel {
    position: fixed;
    top: 85px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--panel-bg);
    border: var(--toolbar-border);
    border-radius: 14px;
    box-shadow: var(--shadow);
    padding: 16px;
    z-index: 1040;
    display: none;
    backdrop-filter: blur(10px);
    max-width: 90vw;
}

#sub-panel-chemicals { width: 620px; }
#sub-panel-apparatus { width: 340px; }

.chemical-partner-guidance {
    min-height: 36px;
    margin: 0 0 12px;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 600;
    line-height: 1.5;
    text-wrap: pretty;
}

.chemical-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    max-height: 280px;
    overflow-y: auto;
    overflow-x: hidden;
    padding-right: 4px;
    box-sizing: border-box;
}

#chem-search-input:focus {
    border-color: #00b0ff;
}

.chemical-card {
    appearance: none;
    background: var(--bg-main);
    border: 1.5px solid var(--text-color);
    border-radius: 8px;
    padding: 8px 4px 7px;
    text-align: center;
    cursor: grab;
    color: var(--text-color);
    font: inherit;
    min-height: 44px;
    transition: transform 0.15s, box-shadow 0.15s, background-color 0.15s;
    box-sizing: border-box;
    min-width: 0;
    width: 100%;
}

.chemical-card:hover {
    transform: translateY(-2px);
    box-shadow: 0px 4px 12px rgba(0,0,0,0.1);
}

.chemical-card[aria-pressed="true"] {
    box-shadow: inset 0 0 0 2px var(--text-color);
}

.chemical-card.compatible-partner {
    background: color-mix(in srgb, var(--text-color) 7%, var(--bg-main));
    box-shadow: inset 0 0 0 2px var(--text-color);
}

.chemical-card:focus-visible,
.apparatus-option-card:focus-visible {
    outline: 3px solid #00b0ff;
    outline-offset: 2px;
}

.chemical-symbol {
    font-size: 16px;
    font-weight: 700;
    display: block;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.chemical-name {
    font-size: 10px;
    opacity: 0.7;
    display: block;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.chemical-card-status {
    width: fit-content;
    max-width: calc(100% - 8px);
    margin: 5px auto 0;
    padding: 2px 5px;
    display: block;
    overflow: hidden;
    border-radius: 999px;
    background: var(--text-color);
    color: var(--bg-main);
    font-size: 8px;
    font-weight: 700;
    line-height: 1.35;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.chemical-card-status[hidden] {
    display: none;
}

.apparatus-selector-wrapper {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.apparatus-option-card {
    appearance: none;
    background: var(--bg-main);
    border: 1.5px solid var(--text-color);
    border-radius: 8px;
    padding: 12px;
    font-weight: 600;
    cursor: pointer;
    color: var(--text-color);
    font: inherit;
    min-height: 44px;
    text-align: center;
    transition: background-color 0.2s, color 0.2s, box-shadow 0.2s;
}

.apparatus-option-card:hover, .apparatus-option-card.selected {
    background: var(--text-color);
    color: var(--bg-main);
}

#canvas-zone {
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
    height: 100vh;
    position: relative;
}

.app-title-card {
    position: absolute;
    top: 92px;
    left: 24px;
    z-index: 100;
    width: min(360px, calc(100vw - 48px));
    padding: 18px 20px 20px;
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
    backdrop-filter: blur(10px);
}

.app-title-card h1 {
    max-width: 18ch;
    font-size: clamp(28px, 2.6vw, 36px);
    font-weight: 700;
    line-height: 1.08;
    margin: 0 0 12px;
    letter-spacing: -1px;
    text-wrap: balance;
}

.app-wordmark {
    margin: 0 0 8px;
    font-size: 13px;
    font-weight: 700;
    letter-spacing: 0.01em;
    opacity: 0.64;
}

.app-subheadline {
    max-width: 42ch;
    margin: 0;
    font-size: 14px;
    line-height: 1.5;
    opacity: 0.76;
    text-wrap: pretty;
}

.ai-sidebar {
    height: 100vh;
    border-left: 2px solid var(--text-color);
    background: var(--bg-main);
    display: flex;
    flex-direction: column;
    z-index: 1020;
}

.lab-instruction {
    color: var(--muted-text);
}

.lab-empty-state {
    max-width: 34ch;
    margin-inline: auto;
}

.lab-demo-link {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 700;
    text-underline-offset: 4px;
}

.lab-demo-link:hover {
    color: var(--text-color);
    text-decoration-thickness: 2px;
}

.lab-demo-link:focus-visible {
    border-radius: 4px;
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.lab-control-arrow {
    display: inline-block;
    font-family: inherit;
    font-size: 1.05em;
    font-weight: 700;
    line-height: 1;
}

.result-heading-mark,
.safety-rule-mark {
    width: 1.1em;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-family: 'Plus Jakarta Sans', sans-serif;
    font-weight: 700;
    line-height: 1;
}

.safety-rule-mark {
    color: var(--text-color);
}

.safety-heading,
.safety-list {
    color: var(--text-color);
}

.reaction-feedback {
    margin-top: 24px;
    padding: 20px 2px 2px;
    border-top: 1px solid var(--border-color);
}

.reaction-feedback-label {
    margin: 0 0 6px;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.02em;
}

.reaction-feedback-title {
    margin: 0 0 10px;
    color: var(--text-color);
    font-size: 16px;
    font-weight: 700;
    line-height: 1.4;
}

.reaction-feedback-link {
    min-height: 44px;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--text-color);
    font-size: 14px;
    font-weight: 700;
    text-underline-offset: 4px;
}

.reaction-feedback-link:hover {
    color: var(--text-color);
    text-decoration-thickness: 2px;
}

.reaction-feedback-link:focus-visible {
    border-radius: 4px;
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.reaction-feedback-note {
    margin: 6px 0 0;
    color: var(--muted-text);
    font-size: 12px;
    line-height: 1.5;
}

.reaction-study {
    margin-top: 24px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.reaction-study-label {
    margin: 0 0 6px;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.02em;
}

.reaction-study-title {
    margin: 0 0 12px;
    color: var(--text-color);
    font-size: 16px;
    font-weight: 700;
    line-height: 1.4;
}

.reaction-study-links {
    display: grid;
    border-top: 1px solid var(--border-color);
}

.reaction-study-links a {
    min-height: 44px;
    padding: 9px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 13px;
    font-weight: 700;
    line-height: 1.45;
    text-decoration: none;
}

.reaction-study-links a:hover {
    text-decoration: underline;
    text-decoration-thickness: 2px;
    text-underline-offset: 4px;
}

.reaction-study-links a:focus-visible {
    border-radius: 4px;
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.response-container {
    flex-grow: 1;
    border: 2px solid var(--text-color);
    border-radius: 12px;
    background: var(--bg-canvas);
    overflow-y: auto;
    padding: 16px;
}

.prediction-input-note {
    max-width: 46ch;
    margin: 0 2px 12px;
    color: var(--muted-text);
    font-size: 12px;
    line-height: 1.5;
    text-wrap: pretty;
}

.analysis-availability-message,
.prediction-input-boundary {
    display: block;
}

.analysis-availability-message {
    color: var(--text-color);
    font-weight: 700;
    margin-bottom: 3px;
}

.action-btn-primary {
    background: var(--text-color);
    color: var(--bg-main);
    border: 2px solid var(--text-color);
    font-weight: 700;
    padding: 12px;
    border-radius: 10px;
    transition: all 0.2s;
}

.action-btn-primary:hover {
    border: 1px solid var(--text-color);
    border-width: 2px;
    opacity: 0.9;
}

.action-btn-primary:disabled,
.action-btn-primary:disabled:hover {
    background: var(--bg-canvas);
    border-color: var(--border-color);
    color: var(--muted-text);
    cursor: not-allowed;
    opacity: 1;
}

.action-btn-secondary {
    background: transparent;
    color: var(--text-color);
    border: 2px solid var(--text-color);
    font-weight: 600;
    border-radius: 8px;
}

.action-btn-secondary:hover {
    background: var(--text-color);
    color: var(--bg-main);
}

.guide-library {
    border-top: 2px solid var(--border-color);
    background: var(--bg-main);
}

.guide-library-shell {
    width: min(1040px, calc(100% - 48px));
    margin: 0 auto;
    padding: 48px 0;
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(280px, 0.72fr);
    align-items: center;
    gap: 48px;
}

.guide-library-context {
    margin: 0 0 12px;
    color: var(--muted-text);
    font-size: 14px;
    font-weight: 700;
}

.guide-library-intro h2 {
    max-width: 17ch;
    margin: 0;
    color: var(--text-color);
    font-size: clamp(32px, 3.3vw, 40px);
    line-height: 1.06;
    letter-spacing: -1.4px;
    text-wrap: balance;
}

.guide-library-description {
    max-width: 39ch;
    margin: 22px 0 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.65;
    text-wrap: pretty;
}

.guide-library-overview-link {
    margin-top: 22px;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--text-color);
    font-size: 14px;
    font-weight: 700;
    text-underline-offset: 4px;
}

.guide-library-overview-link:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.guide-library-summary {
    min-height: 144px;
    padding: 28px;
    display: flex;
    align-items: center;
    gap: 24px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--bg-canvas);
    box-shadow: var(--shadow);
}

.guide-library-count {
    color: var(--text-color);
    font-size: clamp(48px, 6vw, 60px);
    font-weight: 700;
    line-height: 1;
    letter-spacing: -4px;
    font-variant-numeric: tabular-nums;
}

.guide-library-summary p {
    margin: 0;
    display: grid;
    gap: 8px;
}

.guide-library-summary strong {
    color: var(--text-color);
    font-size: 18px;
    line-height: 1.4;
}

.guide-library-summary p span {
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.55;
    text-wrap: pretty;
}

.faq-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
}

.faq-shell {
    width: min(1040px, calc(100% - 48px));
    margin: 0 auto;
    padding: 72px 0 88px;
    display: grid;
    grid-template-columns: minmax(220px, 0.72fr) minmax(0, 1.28fr);
    align-items: start;
    gap: 72px;
}

.faq-intro {
    position: sticky;
    top: 32px;
}

.faq-context {
    margin: 0 0 12px;
    color: var(--muted-text);
    font-size: 14px;
    font-weight: 700;
}

.faq-intro h1 {
    max-width: 12ch;
    margin: 0;
    font-size: clamp(48px, 6vw, 72px);
    line-height: 0.98;
    letter-spacing: -3px;
    text-wrap: balance;
}

.faq-intro > p:last-child {
    max-width: 38ch;
    margin: 24px 0 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.65;
    text-wrap: pretty;
}

.faq-primary {
    box-sizing: border-box;
    min-height: 48px;
    margin-top: 32px;
    padding: 12px 18px;
    display: inline-flex;
    align-items: center;
    justify-content: space-between;
    gap: 32px;
    border: 2px solid var(--text-color);
    border-radius: 10px;
    background: var(--text-color);
    color: var(--bg-main);
    font-size: 14px;
    font-weight: 700;
    text-decoration: none;
    transition: opacity 0.16s ease, transform 0.16s ease;
}

.faq-primary:hover {
    color: var(--bg-main);
    opacity: 0.88;
}

.faq-primary:active {
    transform: translateY(1px);
}

.faq-primary:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.faq-list {
    border-top: 1px solid var(--border-color);
}

.faq-item {
    border-bottom: 1px solid var(--border-color);
}

.faq-item summary {
    min-height: 72px;
    padding: 22px 52px 22px 0;
    position: relative;
    display: flex;
    align-items: center;
    color: var(--text-color);
    font-size: 18px;
    font-weight: 700;
    line-height: 1.4;
    cursor: pointer;
    list-style: none;
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-item summary::after {
    content: "+";
    width: 32px;
    height: 32px;
    position: absolute;
    right: 0;
    display: grid;
    place-items: center;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    font-size: 20px;
    font-weight: 400;
    line-height: 1;
}

.faq-item[open] summary::after {
    content: "\2212";
}

.faq-item summary:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 4px;
}

.faq-item p {
    max-width: 60ch;
    margin: -4px 0 24px;
    padding-right: 48px;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.65;
    text-wrap: pretty;
}

.faq-answer-link {
    color: var(--text-color);
    font-weight: 700;
    text-underline-offset: 4px;
}

.faq-answer-link:hover {
    color: var(--text-color);
    text-decoration-thickness: 2px;
}

.faq-answer-link:focus-visible {
    border-radius: 3px;
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.tin-mark {
    width: 1em;
    height: 1em;
    background: #66dc9d;
    flex: 0 0 auto;
}

@media (max-width: 991.98px) {
    body { overflow-y: auto; height: auto; }
    #canvas-zone { height: 500px; }
    .ai-sidebar { height: auto; border-left: none; border-top: 2px solid var(--text-color); }
    .excalidraw-floating-toolbar {
        position: sticky;
        top: 10px;
        left: 0;
        transform: none;
        margin: 10px auto;
        gap: 4px;
    }
    .toolbar-trigger-btn {
        min-height: 44px;
        min-width: 0;
        padding: 8px 10px;
    }
    .floating-popover-panel { position: absolute; top: 70px; }
    .home-page .excalidraw-floating-toolbar { position: sticky; }
    .home-page .app-title-card:not(.app-title-card--guided) { display: none; }
}

@media (min-width: 1200px) {
    .app-title-card { top: 24px; }
    .home-page .excalidraw-floating-toolbar {
        /* Center the controls between the title card and the lab column edge. */
        left: calc(33.333333% + 192px);
    }
}

.pricing-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
}

.pricing-site-header {
    width: min(1180px, calc(100% - 48px));
    margin: 0 auto;
    padding: 24px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.pricing-brand {
    color: var(--text-color);
    font-size: 20px;
    font-weight: 700;
    letter-spacing: -0.4px;
    text-decoration: none;
}

.pricing-page-label {
    color: var(--muted-text);
    font-size: 14px;
    font-weight: 600;
}

.pricing-shell {
    width: min(1180px, calc(100% - 48px));
    margin: 32px auto 0;
}

.pricing-hero {
    display: grid;
    grid-template-columns: minmax(0, 0.86fr) minmax(0, 1.14fr);
    align-items: center;
    gap: 64px;
}

.pricing-context {
    margin: 0 0 12px;
    color: var(--muted-text);
    font-size: 15px;
    font-weight: 600;
}

.pricing-copy h1 {
    max-width: 13ch;
    margin: 0;
    font-size: clamp(42px, 5vw, 68px);
    line-height: 1.02;
    letter-spacing: -2.5px;
    text-wrap: balance;
}

.pricing-lede {
    max-width: 52ch;
    margin: 24px 0 32px;
    color: var(--muted-text);
    font-size: 17px;
    line-height: 1.6;
    text-wrap: pretty;
}

.pricing-offer {
    max-width: 430px;
    padding: 24px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.pricing-price-line {
    display: flex;
    align-items: baseline;
    gap: 16px;
    margin-bottom: 20px;
}

.pricing-price {
    font-size: 48px;
    font-weight: 700;
    line-height: 1;
    letter-spacing: -2px;
    font-variant-numeric: tabular-nums;
}

.pricing-term {
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.4;
}

.pricing-features {
    margin: 0 0 24px;
    padding: 0;
    display: grid;
    gap: 10px;
    list-style: none;
}

.pricing-features li {
    display: flex;
    gap: 10px;
    font-size: 15px;
    line-height: 1.45;
}

.pricing-features li::before {
    content: "✓";
    font-weight: 700;
}

.pricing-primary {
    min-height: 48px;
    padding: 12px 20px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--text-color);
    border-radius: 10px;
    background: var(--text-color);
    color: var(--bg-main);
    font-weight: 700;
    text-decoration: none;
    transition: opacity 0.16s ease, transform 0.16s ease;
}

.pricing-primary:hover {
    color: var(--bg-main);
    opacity: 0.9;
}

.pricing-primary:active {
    transform: translateY(1px);
}

.pricing-primary:focus-visible,
.pricing-brand:focus-visible,
.pricing-source-link:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.pricing-preview {
    margin: 0;
}

.pricing-preview-frame {
    overflow: hidden;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--bg-main);
    box-shadow: var(--shadow);
}

.pricing-preview img {
    width: 100%;
    height: auto;
    display: block;
}

.pricing-preview figcaption {
    margin-top: 12px;
    color: var(--muted-text);
    font-size: 13px;
    line-height: 1.5;
}

.pricing-open-source {
    margin: 80px 0 64px;
    padding: 32px 0 0;
    display: grid;
    grid-template-columns: minmax(0, 0.7fr) minmax(0, 1.3fr);
    gap: 48px;
    border-top: 1px solid rgba(30, 30, 30, 0.2);
}

.pricing-open-source h2 {
    margin: 0;
    font-size: clamp(28px, 3vw, 40px);
    line-height: 1.1;
    letter-spacing: -1.2px;
}

.pricing-open-source p {
    max-width: 58ch;
    margin: 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.65;
}

.pricing-source-link {
    color: var(--text-color);
    font-weight: 700;
    text-underline-offset: 3px;
}

.site-footer {
    width: min(1180px, calc(100% - 48px));
    margin: 0 auto;
    padding: 24px 0 32px;
    display: flex;
    align-items: center;
    gap: 20px;
    color: var(--muted-text);
    font-size: 12px;
}

.site-footer--floating {
    position: fixed;
    bottom: 8px;
    left: 24px;
    z-index: 1030;
    width: auto;
    margin: 0;
    padding: 0;
}

.site-footer-brand {
    color: var(--text-color) !important;
    font-weight: 700;
}

.site-footer-nav {
    display: flex;
    align-items: center;
    gap: 16px;
}

.site-footer-credit {
    margin-left: auto;
}

.site-footer a {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    color: inherit;
    text-decoration: none;
}

.site-footer a:hover {
    text-decoration: underline;
}

.site-footer a:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.site-footer--floating .site-footer-credit {
    margin-left: 0;
}

.info-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
}

.info-shell {
    width: min(1040px, calc(100% - 48px));
    margin: 48px auto 96px;
}

.info-hero {
    max-width: 760px;
}

.info-hero h1 {
    max-width: 13ch;
    margin: 0;
    font-size: clamp(48px, 7vw, 84px);
    line-height: 0.98;
    letter-spacing: -3.6px;
    text-wrap: balance;
}

.info-lede {
    max-width: 58ch;
    margin: 24px 0 14px;
    color: var(--muted-text);
    font-size: 18px;
    line-height: 1.65;
    text-wrap: pretty;
}

.info-updated {
    margin: 0;
    color: var(--muted-text);
    font-size: 13px;
}

.info-layout {
    margin-top: 80px;
    display: grid;
    grid-template-columns: minmax(220px, 0.65fr) minmax(0, 1.35fr);
    align-items: start;
    gap: 72px;
}

.info-summary {
    position: sticky;
    top: 24px;
    padding: 24px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.info-summary h2 {
    margin: 0 0 18px;
    font-size: 17px;
    letter-spacing: -0.3px;
}

.info-summary ul {
    margin: 0;
    padding: 0;
    display: grid;
    gap: 14px;
    list-style: none;
}

.info-summary li {
    display: flex;
    gap: 10px;
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.55;
}

.info-summary li::before {
    content: "✓";
    color: var(--text-color);
    font-weight: 700;
}

.info-sections {
    display: grid;
    gap: 40px;
}

.info-sections section {
    padding-top: 24px;
    border-top: 1px solid rgba(30, 30, 30, 0.2);
}

.info-sections section:first-child {
    padding-top: 0;
    border-top: 0;
}

.info-sections h2 {
    margin: 0 0 12px;
    font-size: 22px;
    line-height: 1.2;
    letter-spacing: -0.6px;
}

.info-sections p {
    margin: 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.75;
}

.info-sections a {
    color: var(--text-color);
    font-weight: 700;
    text-underline-offset: 3px;
}

.contact-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
}

.contact-shell {
    width: min(1180px, calc(100% - 48px));
    margin: 44px auto 80px;
    display: grid;
    grid-template-columns: minmax(280px, 0.78fr) minmax(520px, 1.22fr);
    align-items: start;
    gap: clamp(56px, 8vw, 112px);
}

.contact-intro {
    position: sticky;
    top: 32px;
}

.contact-intro h1 {
    max-width: 10ch;
    margin: 0;
    font-size: clamp(50px, 6vw, 76px);
    line-height: 0.98;
    letter-spacing: -3.2px;
    text-wrap: balance;
}

.contact-lede {
    max-width: 44ch;
    margin: 24px 0 40px;
    color: var(--muted-text);
    font-size: 17px;
    line-height: 1.7;
    text-wrap: pretty;
}

.contact-expectation {
    max-width: 410px;
    padding-top: 22px;
    display: grid;
    grid-template-columns: 12px 1fr;
    gap: 14px;
    border-top: 1px solid rgba(30, 30, 30, 0.2);
}

.contact-expectation-mark {
    width: 12px;
    height: 12px;
    margin-top: 4px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
}

.contact-expectation h2 {
    margin: 0 0 7px;
    font-size: 14px;
    line-height: 1.4;
}

.contact-expectation p {
    margin: 0;
    color: var(--muted-text);
    font-size: 13px;
    line-height: 1.65;
}

.contact-form-card {
    padding: clamp(24px, 4vw, 42px);
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.contact-form-heading {
    margin-bottom: 30px;
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    gap: 24px;
}

.contact-form-heading h2 {
    margin: 0;
    font-size: clamp(26px, 3vw, 36px);
    letter-spacing: -1px;
}

.contact-step {
    margin: 0;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.contact-alert {
    margin-bottom: 24px;
    padding: 16px 18px;
    display: grid;
    gap: 4px;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    font-size: 14px;
    line-height: 1.5;
}

.contact-alert--success {
    border-color: #2e7651;
    background: rgba(102, 220, 157, 0.15);
}

.contact-alert--error {
    border-color: #b51d32;
    background: rgba(227, 56, 79, 0.09);
}

.contact-alert span {
    color: var(--muted-text);
}

.contact-form {
    display: grid;
    gap: 22px;
}

.contact-field-row {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
}

.contact-field {
    display: grid;
    gap: 8px;
}

.contact-field label {
    font-size: 13px;
    font-weight: 700;
}

.contact-field label span {
    color: var(--muted-text);
    font-weight: 600;
}

.contact-field input,
.contact-field textarea {
    box-sizing: border-box;
    width: 100%;
    padding: 13px 14px;
    border: 2px solid rgba(30, 30, 30, 0.28);
    border-radius: 9px;
    background: var(--bg-main);
    color: var(--text-color);
    font: inherit;
    font-size: 15px;
    line-height: 1.5;
    transition: border-color 0.16s ease, box-shadow 0.16s ease;
}

.contact-field textarea {
    min-height: 166px;
    resize: vertical;
}

.contact-field input:hover,
.contact-field textarea:hover {
    border-color: rgba(30, 30, 30, 0.55);
}

.contact-field input:focus,
.contact-field textarea:focus {
    border-color: var(--border-color);
    box-shadow: 0 0 0 3px rgba(30, 30, 30, 0.11);
    outline: none;
}

.contact-field input[aria-invalid="true"],
.contact-field textarea[aria-invalid="true"] {
    border-color: #b51d32;
}

.contact-field-error {
    color: #a4162a;
    font-size: 12px;
    font-weight: 700;
}

.contact-session-interest {
    margin: 0;
    padding: 0;
    border: 0;
}

.contact-session-interest legend {
    margin-bottom: 10px;
    padding: 0;
    font-size: 13px;
    font-weight: 700;
}

.contact-session-interest legend span {
    color: var(--muted-text);
    font-weight: 600;
}

.contact-session-option {
    min-height: 44px;
    padding: 14px;
    display: grid;
    grid-template-columns: 20px minmax(0, 1fr);
    align-items: start;
    gap: 12px;
    border: 2px solid rgba(30, 30, 30, 0.22);
    border-radius: 9px;
    background: var(--bg-main);
    cursor: pointer;
}

.contact-session-option:hover {
    border-color: rgba(30, 30, 30, 0.5);
}

.contact-session-option:has(input:focus-visible) {
    border-color: var(--border-color);
    box-shadow: 0 0 0 3px rgba(30, 30, 30, 0.11);
}

.contact-session-option input {
    width: 18px;
    height: 18px;
    margin: 2px 0 0;
    accent-color: var(--text-color);
}

.contact-session-option span {
    display: grid;
    gap: 4px;
}

.contact-session-option strong {
    font-size: 13px;
    line-height: 1.5;
}

.contact-session-option small {
    color: var(--muted-text);
    font-size: 12px;
    line-height: 1.55;
}

.contact-submit-row {
    padding-top: 4px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 28px;
}

.contact-submit-row p {
    max-width: 39ch;
    margin: 0;
    color: var(--muted-text);
    font-size: 11px;
    line-height: 1.6;
}

.contact-submit-row a {
    color: var(--text-color);
    font-weight: 700;
}

.contact-submit-row button {
    min-width: 150px;
    min-height: 50px;
    padding: 12px 18px;
    display: inline-flex;
    align-items: center;
    justify-content: space-between;
    gap: 28px;
    border: 2px solid var(--text-color);
    border-radius: 10px;
    background: var(--text-color);
    color: var(--bg-main);
    font: inherit;
    font-size: 14px;
    font-weight: 700;
    cursor: pointer;
    transition: opacity 0.16s ease, transform 0.16s ease;
}

.contact-submit-row button:hover {
    opacity: 0.88;
}

.contact-submit-row button:active {
    transform: translateY(1px);
}

.contact-submit-row button:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

.guide-page {
    min-height: 100vh;
    height: auto;
    overflow-x: hidden;
    overflow-y: auto;
    background-color: var(--bg-canvas);
    background-image: radial-gradient(var(--grid-color) 1.5px, transparent 1.5px);
    background-size: 24px 24px;
}

.guide-site-header {
    width: min(1180px, calc(100% - 48px));
    margin: 0 auto;
    padding: 24px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.guide-brand {
    color: var(--text-color);
    font-size: 20px;
    font-weight: 700;
    letter-spacing: -0.4px;
    text-decoration: none;
}

.guide-site-label,
.guide-breadcrumb {
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 600;
}

.guide-shell {
    width: min(1180px, calc(100% - 48px));
    margin: 28px auto 0;
}

.guide-breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
}

.guide-breadcrumb a {
    color: var(--text-color);
    text-underline-offset: 3px;
}

.guide-hero {
    margin-top: 44px;
    display: grid;
    grid-template-columns: minmax(0, 0.9fr) minmax(420px, 1.1fr);
    align-items: center;
    gap: 72px;
}

.guide-context,
.guide-section-label {
    margin: 0 0 12px;
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 700;
}

.guide-hero h1 {
    max-width: 13ch;
    margin: 0;
    font-size: clamp(44px, 5.4vw, 72px);
    line-height: 0.99;
    letter-spacing: -3px;
    text-wrap: balance;
}

.guide-answer {
    max-width: 54ch;
    margin: 28px 0 30px;
    color: var(--muted-text);
    font-size: 18px;
    line-height: 1.65;
    text-wrap: pretty;
}

.guide-student-job {
    max-width: 54ch;
    margin: -12px 0 24px;
    padding: 12px 14px;
    border-left: 3px solid var(--text-color);
    background: var(--panel-bg);
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.6;
    text-wrap: pretty;
}

.guide-student-job strong {
    color: var(--text-color);
}

.guide-primary {
    min-height: 52px;
    max-width: 100%;
    padding: 14px 20px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 18px;
    box-sizing: border-box;
    border: 2px solid var(--text-color);
    border-radius: 10px;
    background: var(--text-color);
    color: var(--bg-main);
    font-size: 15px;
    font-weight: 700;
    text-align: center;
    text-decoration: none;
    transition: opacity 0.16s ease, transform 0.16s ease;
}

.guide-primary:hover {
    color: var(--bg-main);
    opacity: 0.9;
}

.guide-primary:active {
    transform: translateY(1px);
}

.guide-cta-note {
    margin: 10px 0 0;
    color: var(--muted-text);
    font-size: 12px;
    line-height: 1.5;
}

.guide-preview {
    margin: 0;
}

.guide-preview-frame {
    position: relative;
    overflow: hidden;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--bg-main);
    box-shadow: var(--shadow);
}

.guide-preview img {
    width: 100%;
    height: auto;
    display: block;
}

.guide-preview-label {
    position: absolute;
    right: 12px;
    bottom: 12px;
    padding: 7px 10px;
    border-radius: 7px;
    background: rgba(30, 30, 30, 0.92);
    color: #ffffff;
    font-size: 11px;
    font-weight: 700;
}

.guide-preview figcaption {
    max-width: 58ch;
    margin-top: 12px;
    color: var(--muted-text);
    font-size: 13px;
    line-height: 1.55;
}

.guide-index-shell {
    width: min(1180px, calc(100% - 48px));
    margin: 28px auto 0;
}

.guide-index-hero {
    margin-top: 44px;
    display: grid;
    grid-template-columns: minmax(0, 0.92fr) minmax(420px, 1.08fr);
    align-items: center;
    gap: 72px;
}

.guide-index-hero h1 {
    max-width: 14ch;
    margin: 0;
    font-size: clamp(44px, 5.4vw, 72px);
    line-height: 0.99;
    letter-spacing: -3px;
    text-wrap: balance;
}

.guide-index-hero-copy > p:not(.guide-context, .guide-cta-note) {
    max-width: 55ch;
    margin: 28px 0 30px;
    color: var(--muted-text);
    font-size: 18px;
    line-height: 1.65;
    text-wrap: pretty;
}

.guide-index-preview {
    margin: 0;
}

.guide-index-preview .guide-preview-frame img {
    width: 100%;
    height: auto;
    display: block;
}

.guide-index-preview figcaption {
    max-width: 58ch;
    margin-top: 12px;
    color: var(--muted-text);
    font-size: 13px;
    line-height: 1.55;
}

.guide-index-library {
    margin-top: 112px;
    display: grid;
    grid-template-columns: minmax(220px, 0.68fr) minmax(0, 1.32fr);
    align-items: start;
    gap: 72px;
}

.guide-index-library-intro {
    position: sticky;
    top: 32px;
}

.guide-index-library-intro h2 {
    max-width: 12ch;
    margin: 0;
    font-size: clamp(34px, 4vw, 48px);
    line-height: 1.06;
    letter-spacing: -1.8px;
    text-wrap: balance;
}

.guide-index-library-intro > p:last-child {
    max-width: 38ch;
    margin: 22px 0 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.65;
    text-wrap: pretty;
}

.guide-index-groups {
    border-top: 2px solid var(--border-color);
}

.guide-index-group {
    padding: 32px 0 64px;
    border-bottom: 2px solid var(--border-color);
}

.guide-index-group > header {
    margin-bottom: 26px;
    display: grid;
    grid-template-columns: 38px minmax(0, 1fr);
    gap: 16px;
}

.guide-index-group-number {
    margin: 3px 0 0;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.04em;
}

.guide-index-group h3 {
    margin: 0;
    font-size: 24px;
    line-height: 1.2;
    letter-spacing: -0.5px;
}

.guide-index-group header div > p {
    max-width: 55ch;
    margin: 10px 0 0;
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.6;
    text-wrap: pretty;
}

.guide-index-list {
    border-top: 1px solid var(--border-color);
}

.guide-index-link {
    min-height: 112px;
    padding: 22px 0;
    display: grid;
    grid-template-columns: 38px minmax(0, 1fr) 24px;
    align-items: center;
    gap: 16px;
    border-bottom: 1px solid rgba(30, 30, 30, 0.24);
    color: var(--text-color);
    text-decoration: none;
}

.guide-index-group--first .guide-index-link {
    min-height: 136px;
}

.guide-index-link-number {
    align-self: start;
    padding-top: 4px;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.04em;
}

.guide-index-link-copy {
    display: grid;
    gap: 8px;
}

.guide-index-link-copy strong {
    font-size: 18px;
    line-height: 1.4;
}

.guide-index-group--first .guide-index-link-copy strong {
    font-size: 22px;
}

.guide-index-link-copy > span {
    max-width: 58ch;
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.6;
    text-wrap: pretty;
}

.guide-index-link-arrow {
    font-size: 20px;
    transition: transform 0.16s ease;
}

.guide-index-link:hover {
    color: var(--text-color);
}

.guide-index-link:hover .guide-index-link-arrow {
    transform: translateX(4px);
}

.guide-index-link:focus-visible {
    border-radius: 4px;
    outline: 3px solid #e3384f;
    outline-offset: 4px;
}

.guide-index-boundary {
    margin-top: 96px;
    padding: 36px 40px;
    display: grid;
    grid-template-columns: minmax(160px, 0.42fr) minmax(0, 1.58fr);
    gap: 48px;
    border-radius: 14px;
    background: var(--text-color);
    color: var(--bg-main);
}

.guide-index-boundary .guide-section-label {
    color: var(--bg-main);
    opacity: 0.7;
}

.guide-index-boundary h2 {
    max-width: 24ch;
    margin: 0;
    font-size: clamp(28px, 3vw, 40px);
    line-height: 1.12;
    letter-spacing: -1.2px;
    text-wrap: balance;
}

.guide-index-boundary div > p {
    max-width: 68ch;
    margin: 18px 0 0;
    color: var(--bg-main);
    font-size: 15px;
    line-height: 1.7;
    opacity: 0.78;
    text-wrap: pretty;
}

.guide-equation {
    margin-top: 96px;
    padding: 30px 32px;
    display: grid;
    grid-template-columns: minmax(0, 1.1fr) minmax(280px, 0.9fr);
    align-items: center;
    gap: 48px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.guide-equation h2 {
    margin: 0;
    font-size: clamp(26px, 3vw, 40px);
    line-height: 1.15;
    letter-spacing: -1.4px;
    text-wrap: balance;
}

.guide-equation > p {
    max-width: 46ch;
    margin: 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.65;
}

.guide-learning {
    margin-top: 104px;
    display: grid;
    grid-template-columns: minmax(240px, 0.72fr) minmax(0, 1.28fr);
    align-items: start;
    gap: 80px;
}

.guide-learning-intro {
    position: sticky;
    top: 32px;
}

.guide-learning-intro h2,
.guide-observe h2,
.guide-boundary h2 {
    margin: 0;
    font-size: clamp(30px, 3.8vw, 48px);
    line-height: 1.04;
    letter-spacing: -1.8px;
    text-wrap: balance;
}

.guide-learning-intro > p:last-child {
    max-width: 38ch;
    margin: 20px 0 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.65;
}

.guide-steps {
    margin: 0;
    padding: 0;
    display: grid;
    list-style: none;
    border-top: 1px solid rgba(30, 30, 30, 0.22);
}

.guide-steps li {
    padding: 30px 0;
    display: grid;
    grid-template-columns: 48px minmax(0, 1fr);
    gap: 20px;
    border-bottom: 1px solid rgba(30, 30, 30, 0.22);
}

.guide-step-number {
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
}

.guide-steps h3 {
    margin: 0 0 9px;
    font-size: 21px;
    line-height: 1.3;
    letter-spacing: -0.5px;
}

.guide-steps p {
    max-width: 60ch;
    margin: 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.7;
    text-wrap: pretty;
}

.guide-notes {
    margin-top: 104px;
    margin-bottom: 64px;
    display: grid;
    grid-template-columns: minmax(0, 0.82fr) minmax(0, 1.18fr);
    gap: 64px;
}

.guide-observe {
    padding-top: 28px;
    border-top: 2px solid var(--border-color);
}

.guide-observe h2 {
    max-width: 14ch;
    font-size: clamp(30px, 3.2vw, 42px);
}

.guide-observe ul {
    margin: 26px 0 0;
    padding: 0;
    display: grid;
    gap: 14px;
    list-style: none;
}

.guide-observe li {
    display: flex;
    gap: 12px;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.55;
}

.guide-observe li::before {
    content: "✓";
    color: var(--text-color);
    font-weight: 700;
}

.guide-boundary {
    padding: 32px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.guide-boundary h2 {
    max-width: 16ch;
    font-size: clamp(30px, 3.2vw, 42px);
}

.guide-boundary > p {
    max-width: 60ch;
    margin: 22px 0 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.7;
}

.guide-boundary .guide-boundary-warning {
    color: var(--text-color);
    font-weight: 700;
}

.guide-sources {
    margin-top: 26px;
    padding-top: 20px;
    display: flex;
    flex-wrap: wrap;
    gap: 8px 16px;
    border-top: 1px solid rgba(30, 30, 30, 0.22);
    color: var(--muted-text);
    font-size: 12px;
    line-height: 1.5;
}

.guide-sources span {
    width: 100%;
    font-weight: 700;
}

.guide-sources a {
    color: var(--text-color);
    font-weight: 700;
    text-underline-offset: 3px;
}

.guide-related {
    margin-bottom: 80px;
    padding-top: 28px;
    display: grid;
    grid-template-columns: minmax(220px, 0.72fr) minmax(0, 1.28fr);
    gap: 64px;
    border-top: 2px solid var(--border-color);
}

.guide-related h2 {
    max-width: 12ch;
    margin: 0;
    font-size: clamp(26px, 3vw, 38px);
    line-height: 1.08;
    letter-spacing: -1.3px;
    text-wrap: balance;
}

.guide-related-links {
    display: grid;
    border-top: 1px solid rgba(30, 30, 30, 0.22);
}

.guide-related-links a {
    min-height: 72px;
    padding: 14px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    border-bottom: 1px solid rgba(30, 30, 30, 0.22);
    color: var(--text-color);
    font-size: 15px;
    line-height: 1.45;
    text-decoration: none;
}

.guide-related-link-copy {
    display: grid;
    gap: 3px;
}

.guide-related-link-copy strong {
    font-size: 15px;
    font-weight: 700;
}

.guide-related-link-copy small {
    color: var(--muted-text);
    font-size: 12px;
    font-weight: 400;
    line-height: 1.45;
}

.guide-related-links a:hover {
    text-decoration: underline;
    text-decoration-thickness: 2px;
    text-underline-offset: 4px;
}

.reaction-lab-shell { width: min(1180px, calc(100% - 48px)); margin: 28px auto 0; }
.reaction-lab-hero { margin-top: 44px; display: grid; grid-template-columns: minmax(0, .92fr) minmax(420px, 1.08fr); align-items: center; gap: 72px; }
.reaction-lab-hero h1 { max-width: 12ch; margin: 0; font-size: clamp(48px, 6vw, 80px); line-height: .96; letter-spacing: -3.5px; text-wrap: balance; }
.reaction-lab-lede { max-width: 56ch; margin: 28px 0 30px; color: var(--muted-text); font-size: 18px; line-height: 1.68; text-wrap: pretty; }
.reaction-lab-preview { transform: rotate(.7deg); }
.reaction-lab-output { margin-top: 96px; padding: 34px 36px; display: grid; grid-template-columns: minmax(220px, .68fr) minmax(0, 1.32fr); gap: 64px; border: 2px solid var(--border-color); border-radius: 14px; background: var(--panel-bg); box-shadow: var(--shadow); }
.reaction-lab-output h2, .reaction-lab-section-intro h2, .reaction-lab-reading-copy h2, .reaction-lab-boundary h2, .reaction-lab-final h2 { margin: 0; font-size: clamp(32px, 4vw, 50px); line-height: 1.04; letter-spacing: -1.9px; text-wrap: balance; }
.reaction-lab-output-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 28px; }
.reaction-lab-output-grid > div { padding: 18px 0 22px; border-top: 1px solid rgba(30, 30, 30, .22); }
.reaction-lab-output-grid span, .reaction-pair-type { color: var(--muted-text); font-size: 11px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.reaction-lab-output-grid h3 { margin: 9px 0 8px; font-size: 17px; }
.reaction-lab-output-grid p, .reaction-lab-section-intro > p:last-child, .reaction-lab-how-list p, .reaction-pair-grid article > p:last-child, .reaction-lab-reading-copy p, .reaction-lab-fit-grid p, .reaction-lab-boundary p, .reaction-lab-final > p { margin: 0; color: var(--muted-text); font-size: 15px; line-height: 1.68; text-wrap: pretty; }
.reaction-lab-how, .reaction-lab-pairs, .reaction-lab-fit, .reaction-lab-faq { margin-top: 112px; display: grid; grid-template-columns: minmax(240px, .7fr) minmax(0, 1.3fr); align-items: start; gap: 80px; }
.reaction-lab-section-intro { position: sticky; top: 32px; }
.reaction-lab-section-intro > p:last-child { max-width: 40ch; margin-top: 20px; }
.reaction-lab-how-list { margin: 0; padding: 0; border-top: 2px solid var(--border-color); list-style: none; }
.reaction-lab-how-list li { padding: 30px 0; display: grid; grid-template-columns: 52px minmax(0, 1fr); gap: 20px; border-bottom: 1px solid rgba(30, 30, 30, .22); }
.reaction-lab-how-list > li > span { width: 36px; height: 36px; display: inline-flex; align-items: center; justify-content: center; border: 2px solid var(--border-color); border-radius: 50%; font-size: 13px; font-weight: 700; }
.reaction-lab-how-list h3 { margin: 3px 0 9px; font-size: 22px; letter-spacing: -.5px; }
.reaction-pair-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; }
.reaction-pair-grid article { min-height: 220px; padding: 24px; display: flex; flex-direction: column; border: 2px solid var(--border-color); border-radius: 12px; background: var(--panel-bg); box-shadow: var(--shadow); }
.reaction-pair-grid article:nth-child(2n) { transform: translateY(12px); }
.reaction-pair-type { margin: 0 0 14px; }
.reaction-pair-grid h3 { margin: 0 0 12px; font-size: 19px; line-height: 1.3; }
.reaction-pair-equation { margin: 0 0 16px; padding: 10px 12px; border-radius: 8px; background: var(--bg-canvas); font-size: 13px; font-weight: 700; line-height: 1.5; }
.reaction-pair-grid article > p:last-child { margin-top: auto; }
.reaction-lab-reading { margin-top: 124px; display: grid; grid-template-columns: minmax(0, 1.08fr) minmax(320px, .92fr); align-items: center; gap: 72px; }
.reaction-lab-equation-card { padding: 32px; border: 2px solid var(--border-color); border-radius: 14px; background: var(--text-color); color: var(--bg-main); box-shadow: var(--shadow); }
.reaction-lab-equation-card .guide-section-label { color: var(--bg-main); opacity: .7; }
.reaction-lab-equation { margin: 30px 0; font-size: clamp(24px, 3.2vw, 39px); font-weight: 700; line-height: 1.28; letter-spacing: -1.3px; }
.reaction-lab-equation-key { padding-top: 20px; display: flex; flex-wrap: wrap; gap: 12px 20px; border-top: 1px solid rgba(255,255,255,.3); font-size: 12px; }
.reaction-lab-reading-copy p { margin-top: 18px; }
.reaction-lab-fit-grid { display: grid; border-top: 2px solid var(--border-color); }
.reaction-lab-fit-grid article { padding: 28px 0; display: grid; grid-template-columns: minmax(200px, .72fr) minmax(0, 1.28fr); gap: 36px; border-bottom: 1px solid rgba(30,30,30,.22); }
.reaction-lab-fit-grid h3 { margin: 0; font-size: 19px; line-height: 1.4; }
.reaction-lab-boundary { margin-top: 112px; padding: 40px; display: grid; grid-template-columns: minmax(260px, .8fr) minmax(0, 1.2fr); gap: 72px; border: 2px solid var(--border-color); border-radius: 14px; background: var(--panel-bg); box-shadow: var(--shadow); }
.reaction-lab-boundary > div:last-child { display: grid; gap: 18px; }
.reaction-lab-boundary .reaction-lab-boundary-strong { color: var(--text-color); font-weight: 700; }
.reaction-lab-faq-list { border-top: 2px solid var(--border-color); }
.reaction-lab-faq-list details { border-bottom: 1px solid rgba(30,30,30,.22); }
.reaction-lab-faq-list summary { min-height: 72px; padding: 20px 42px 20px 0; position: relative; display: flex; align-items: center; cursor: pointer; font-size: 17px; font-weight: 700; line-height: 1.4; list-style: none; }
.reaction-lab-faq-list summary::-webkit-details-marker { display: none; }
.reaction-lab-faq-list summary::after { content: "+"; position: absolute; right: 4px; font-size: 22px; }
.reaction-lab-faq-list details[open] summary::after { content: "−"; }
.reaction-lab-faq-list details p { max-width: 66ch; margin: -2px 0 24px; color: var(--muted-text); font-size: 15px; line-height: 1.7; }
.reaction-lab-final { margin-top: 112px; padding: 48px; border-radius: 14px; background: var(--text-color); color: var(--bg-main); }
.reaction-lab-final h2 { max-width: 19ch; }
.reaction-lab-final .guide-section-label, .reaction-lab-final > p { color: var(--bg-main); opacity: .78; }
.reaction-lab-final > p { max-width: 64ch; margin-top: 18px; }
.reaction-lab-final-links { margin-top: 28px; display: flex; align-items: center; flex-wrap: wrap; gap: 16px 24px; }
.reaction-lab-final .guide-primary { border-color: var(--bg-main); background: var(--bg-main); color: var(--text-color); }
.reaction-lab-final-links > a:last-child { color: var(--bg-main); font-size: 14px; font-weight: 700; text-underline-offset: 4px; }
.reaction-lab-related { margin-top: 80px; }

.observation-guide-shell {
    width: min(1180px, calc(100% - 48px));
    margin: 28px auto 0;
}

.observation-guide-hero {
    margin-top: 44px;
    display: grid;
    grid-template-columns: minmax(0, .92fr) minmax(440px, 1.08fr);
    align-items: center;
    gap: 72px;
}

.observation-guide-hero h1 {
    max-width: 14ch;
    margin: 0;
    font-size: clamp(44px, 5.4vw, 70px);
    line-height: .99;
    letter-spacing: -3px;
    text-wrap: balance;
}

.observation-guide-preview {
    margin: 0;
}

.observation-guide-preview-frame {
    position: relative;
    min-height: 370px;
    overflow: hidden;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.observation-guide-preview-frame img {
    width: 100%;
    height: 370px;
    display: block;
    object-fit: cover;
    object-position: 58% center;
    opacity: .72;
}

.observation-guide-setup-card {
    position: absolute;
    right: 20px;
    bottom: 20px;
    left: 20px;
    padding: 20px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.observation-guide-setup-card > span,
.observation-guide-setup-card small {
    color: var(--muted-text);
    font-size: 11px;
    font-weight: 700;
}

.observation-guide-reactants {
    margin: 10px 0;
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: clamp(20px, 2.8vw, 32px);
    letter-spacing: -1px;
}

.observation-guide-preview figcaption {
    max-width: 64ch;
    margin-top: 12px;
    color: var(--muted-text);
    font-size: 13px;
    line-height: 1.55;
}

.observation-guide-result {
    margin-top: 96px;
    padding: 36px;
    display: grid;
    grid-template-columns: minmax(0, 1.08fr) minmax(300px, .92fr);
    align-items: start;
    gap: 56px;
    border: 2px solid var(--border-color);
    border-radius: 14px;
    background: var(--text-color);
    color: var(--bg-main);
    box-shadow: var(--shadow);
}

.observation-guide-result .guide-section-label {
    color: var(--bg-main);
    opacity: .68;
}

.observation-guide-equation h2 {
    margin: 0;
    font-size: clamp(25px, 3.2vw, 41px);
    line-height: 1.25;
    letter-spacing: -1.4px;
    text-wrap: balance;
}

.observation-guide-explanation {
    padding-left: 28px;
    border-left: 1px solid rgba(255, 255, 255, .3);
}

.observation-guide-explanation p:last-child {
    max-width: 52ch;
    margin: 0;
    color: var(--bg-main);
    font-size: 15px;
    line-height: 1.72;
    opacity: .82;
    text-wrap: pretty;
}

.observation-guide-observation {
    margin-top: 112px;
    display: grid;
    grid-template-columns: minmax(0, .92fr) minmax(340px, 1.08fr);
    align-items: center;
    gap: 88px;
}

.observation-guide-observation-copy h2,
.observation-guide-safety h2,
.observation-guide-next h2 {
    max-width: 15ch;
    margin: 0;
    font-size: clamp(34px, 4.3vw, 54px);
    line-height: 1.03;
    letter-spacing: -2px;
    text-wrap: balance;
}

.observation-guide-observation-copy > p:last-child,
.observation-guide-next > div > p {
    max-width: 54ch;
    margin: 22px 0 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.7;
    text-wrap: pretty;
}

.observation-vessel {
    width: min(100%, 440px);
    height: 340px;
    margin: 0 auto;
    position: relative;
    display: flex;
    align-items: flex-end;
    justify-content: center;
}

.observation-vessel::before {
    content: "";
    position: absolute;
    right: 42px;
    bottom: 28px;
    left: 42px;
    height: 260px;
    border: 4px solid var(--border-color);
    border-top: 0;
    border-radius: 0 0 44px 44px;
    background: rgba(255, 255, 255, .56);
}

.observation-vessel-rim {
    position: absolute;
    top: 48px;
    right: 24px;
    left: 24px;
    height: 24px;
    z-index: 2;
    border: 4px solid var(--border-color);
    border-radius: 50%;
    background: var(--bg-canvas);
}

.observation-vessel-liquid {
    position: absolute;
    right: 46px;
    bottom: 32px;
    left: 46px;
    height: 152px;
    overflow: hidden;
    border-radius: 0 0 39px 39px;
    background: rgba(125, 156, 183, .24);
}

.observation-vessel strong {
    position: relative;
    z-index: 3;
    margin-bottom: 52px;
    padding: 7px 10px;
    border-radius: 7px;
    background: rgba(30, 30, 30, .9);
    color: #fff;
    font-size: 12px;
}

.observation-particle {
    position: absolute;
    width: 34px;
    height: 14px;
    border-radius: 50%;
    background: #f5f3ea;
}

.particle-one { right: 18%; bottom: 20%; }
.particle-two { right: 40%; bottom: 42%; width: 22px; }
.particle-three { left: 16%; bottom: 30%; width: 42px; }
.particle-four { left: 43%; bottom: 12%; width: 48px; }
.particle-five { right: 28%; bottom: 5%; width: 30px; }

.observation-cloudy .observation-vessel-liquid {
    background: rgba(245, 243, 234, .76);
}

.observation-yellow .observation-vessel-liquid {
    background: rgba(242, 201, 76, .28);
}

.observation-yellow .observation-particle {
    background: #f2c94c;
}

.observation-blue .observation-vessel-liquid {
    background: rgba(91, 167, 209, .3);
}

.observation-blue .observation-particle {
    background: #5ba7d1;
}

.observation-clear .observation-vessel-liquid {
    background: rgba(177, 218, 238, .32);
}

.observation-clear .observation-particle {
    display: none;
}

.observation-bubbles .observation-particle {
    width: 24px;
    height: 24px;
    border: 3px solid rgba(30, 30, 30, .62);
    background: transparent;
}

.observation-bubbles .particle-two,
.observation-bubbles .particle-five {
    width: 14px;
    height: 14px;
}

.observation-guide-ions {
    margin-top: 112px;
    padding-top: 28px;
    display: grid;
    grid-template-columns: minmax(0, .92fr) minmax(340px, 1.08fr);
    align-items: start;
    gap: 72px;
    border-top: 2px solid var(--border-color);
}

.observation-guide-ions-intro h2 {
    max-width: 14ch;
    margin: 0;
    font-size: clamp(34px, 4.3vw, 54px);
    line-height: 1.03;
    letter-spacing: -2px;
    text-wrap: balance;
}

.observation-guide-ions-intro > p:not(.guide-section-label, .observation-guide-spectators) {
    max-width: 58ch;
    margin: 22px 0 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.7;
}

.observation-guide-ionic-equation {
    margin-top: 32px;
    padding: 24px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    background: var(--text-color);
    color: var(--bg-main);
    box-shadow: var(--shadow);
}

.observation-guide-ionic-equation span {
    display: block;
    margin-bottom: 10px;
    color: var(--bg-main);
    font-size: 11px;
    font-weight: 700;
    opacity: .68;
}

.observation-guide-ionic-equation strong {
    display: block;
    font-size: clamp(20px, 2.5vw, 29px);
    line-height: 1.3;
    letter-spacing: -.7px;
}

.observation-guide-spectators {
    margin: 18px 0 0;
    color: var(--muted-text);
    font-size: 14px;
}

.observation-guide-ion-steps {
    margin: 0;
    padding: 0;
    border-top: 1px solid rgba(30, 30, 30, .22);
    list-style: none;
}

.observation-guide-ion-steps li {
    min-height: 112px;
    padding: 24px 0;
    display: grid;
    grid-template-columns: 48px minmax(0, 1fr);
    align-items: start;
    gap: 16px;
    border-bottom: 1px solid rgba(30, 30, 30, .22);
}

.observation-guide-ion-steps li > span {
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
}

.observation-guide-ion-steps h3 {
    margin: 0;
    font-size: 18px;
    line-height: 1.35;
}

.observation-guide-ion-steps p {
    max-width: 56ch;
    margin: 9px 0 0;
    color: var(--muted-text);
    font-size: 14px;
    line-height: 1.65;
}

.observation-guide-study,
.observation-guide-details,
.observation-guide-questions {
    margin-top: 112px;
}

.observation-guide-study-intro,
.observation-guide-details-intro,
.observation-guide-questions-intro {
    max-width: 720px;
}

.observation-guide-study-intro h2,
.observation-guide-details-intro h2,
.observation-guide-questions-intro h2 {
    max-width: 17ch;
    margin: 12px 0 16px;
    color: var(--text-color);
    font-size: clamp(34px, 4vw, 52px);
    line-height: 1.04;
    letter-spacing: -2px;
    text-wrap: balance;
}

.observation-guide-study-intro > p:last-child,
.observation-guide-details-intro > p:last-child,
.observation-guide-questions-intro > p:last-child {
    max-width: 650px;
    margin: 0;
    color: var(--muted-text);
    font-size: 16px;
    line-height: 1.75;
}

.observation-guide-study-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
    margin: 36px 0 0;
    padding: 0;
    list-style: none;
}

.observation-guide-study-grid li,
.observation-guide-question-list article {
    padding: 28px;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    background: var(--panel-bg);
    box-shadow: var(--shadow);
}

.observation-guide-study-grid li > span,
.observation-guide-detail-list article > span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 34px;
    height: 34px;
    flex: 0 0 34px;
    border-radius: 50%;
    background: var(--text-color);
    color: var(--bg-main);
    font-size: 12px;
    font-weight: 700;
}

.observation-guide-study-grid h3,
.observation-guide-detail-list h3,
.observation-guide-question-list h3 {
    margin: 22px 0 10px;
    color: var(--text-color);
    font-size: 19px;
    line-height: 1.35;
}

.observation-guide-study-grid p,
.observation-guide-detail-list p,
.observation-guide-question-list p {
    margin: 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.7;
}

.observation-guide-details,
.observation-guide-questions {
    display: grid;
    grid-template-columns: minmax(260px, .72fr) minmax(0, 1.28fr);
    gap: 64px;
    align-items: start;
    padding-top: 28px;
    border-top: 2px solid var(--border-color);
}

.observation-guide-detail-list article {
    padding: 24px 0;
    display: flex;
    align-items: flex-start;
    gap: 18px;
    border-bottom: 1px solid rgba(30, 30, 30, .22);
}

.observation-guide-detail-list article:first-child {
    border-top: 1px solid rgba(30, 30, 30, .22);
}

.observation-guide-detail-list h3 {
    margin-top: 2px;
}

.observation-guide-question-list {
    display: grid;
    gap: 12px;
}

.observation-guide-question-list h3 {
    margin-top: 0;
}

.observation-guide-notes {
    margin-top: 112px;
    display: grid;
    grid-template-columns: minmax(0, 1.08fr) minmax(340px, .92fr);
    align-items: start;
    gap: 72px;
}

.observation-guide-safety {
    padding-top: 28px;
    border-top: 2px solid var(--border-color);
}

.observation-guide-safety ol {
    margin: 34px 0 0;
    padding: 0;
    border-top: 1px solid rgba(30, 30, 30, .22);
    list-style: none;
}

.observation-guide-safety li {
    min-height: 80px;
    padding: 18px 0;
    display: grid;
    grid-template-columns: 48px minmax(0, 1fr);
    align-items: start;
    gap: 16px;
    border-bottom: 1px solid rgba(30, 30, 30, .22);
}

.observation-guide-safety li span {
    color: var(--muted-text);
    font-size: 13px;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
}

.observation-guide-safety li p {
    max-width: 58ch;
    margin: 0;
    color: var(--muted-text);
    font-size: 15px;
    line-height: 1.65;
}

.observation-guide-next {
    margin: 112px 0 80px;
    padding-top: 28px;
    display: grid;
    grid-template-columns: minmax(260px, .82fr) minmax(0, 1.18fr);
    gap: 72px;
    border-top: 2px solid var(--border-color);
}

.observation-guide-next > div > a {
    min-height: 44px;
    margin-top: 18px;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--text-color);
    font-size: 14px;
    font-weight: 700;
    text-underline-offset: 4px;
}

.guide-primary:focus-visible,
.guide-brand:focus-visible,
.guide-breadcrumb a:focus-visible,
.guide-sources a:focus-visible,
.observation-guide-next > div > a:focus-visible,
.guide-related-links a:focus-visible {
    outline: 3px solid #e3384f;
    outline-offset: 3px;
}

@media (max-width: 900px) {
    .pricing-shell { margin-top: 16px; }
    .pricing-hero { grid-template-columns: 1fr; gap: 48px; }
    .pricing-copy h1 { max-width: 15ch; }
    .pricing-offer { max-width: none; }
    .pricing-open-source { grid-template-columns: 1fr; gap: 16px; }
    .info-layout { grid-template-columns: 1fr; gap: 48px; }
    .info-summary { position: static; }
    .guide-library-shell { grid-template-columns: 1fr; gap: 48px; }
    .guide-library-intro h2 { max-width: 16ch; }
    .faq-shell { grid-template-columns: 1fr; gap: 48px; }
    .faq-intro { position: static; }
    .faq-intro h1 { max-width: 14ch; }
    .guide-hero { grid-template-columns: 1fr; gap: 48px; }
    .guide-hero h1 { max-width: 15ch; }
    .guide-index-hero { grid-template-columns: 1fr; gap: 48px; }
    .guide-index-hero h1 { max-width: 15ch; }
    .guide-index-library { grid-template-columns: 1fr; gap: 48px; }
    .guide-index-library-intro { position: static; }
    .guide-index-library-intro h2 { max-width: 15ch; }
    .guide-index-boundary { grid-template-columns: 1fr; gap: 20px; }
    .guide-equation { grid-template-columns: 1fr; gap: 20px; }
    .guide-learning { grid-template-columns: 1fr; gap: 48px; }
    .guide-learning-intro { position: static; }
    .guide-notes { grid-template-columns: 1fr; gap: 48px; }
    .guide-related { grid-template-columns: 1fr; gap: 28px; }
    .reaction-lab-hero, .reaction-lab-output, .reaction-lab-how, .reaction-lab-pairs, .reaction-lab-reading, .reaction-lab-fit, .reaction-lab-faq, .reaction-lab-boundary { grid-template-columns: 1fr; gap: 48px; }
    .reaction-lab-section-intro { position: static; }
    .reaction-lab-preview { transform: none; }
    .observation-guide-hero,
    .observation-guide-result,
    .observation-guide-observation,
    .observation-guide-ions,
    .observation-guide-details,
    .observation-guide-questions,
    .observation-guide-notes,
    .observation-guide-next {
        grid-template-columns: 1fr;
        gap: 48px;
    }
    .observation-guide-study-grid { grid-template-columns: 1fr; }
    .observation-guide-explanation {
        padding: 24px 0 0;
        border-top: 1px solid rgba(255, 255, 255, .3);
        border-left: 0;
    }
    .contact-shell { grid-template-columns: 1fr; gap: 48px; }
    .contact-intro { position: static; }
    .contact-intro h1 { max-width: 13ch; }
}

@media (max-width: 991.98px) {
    .site-footer--floating {
        position: static;
        width: auto;
        margin: 16px 24px;
        padding: 0;
    }
}

@media (max-width: 560px) {
    .pricing-site-header,
    .pricing-shell,
    .site-footer,
    .info-shell,
    .contact-shell,
    .guide-library-shell,
    .faq-shell,
    .guide-index-shell { width: min(100% - 32px, 1180px); }
    .pricing-site-header { padding: 20px 0; }
    .pricing-shell { margin-top: 8px; }
    .pricing-copy h1 { font-size: 42px; letter-spacing: -1.7px; }
    .pricing-lede { margin: 20px 0 24px; font-size: 16px; }
    .pricing-offer { padding: 20px; }
    .pricing-open-source { margin: 56px 0 40px; }
    .site-footer { align-items: flex-start; flex-wrap: wrap; gap: 14px 20px; }
    .site-footer-nav { width: 100%; flex-wrap: wrap; gap: 12px 16px; order: 2; }
    .site-footer-credit { margin-left: auto; }
    .site-footer--floating { width: auto; margin: 16px; }
    .info-shell { margin-top: 24px; margin-bottom: 64px; }
    .info-hero h1 { font-size: 48px; letter-spacing: -2.2px; }
    .info-lede { font-size: 16px; }
    .info-layout { margin-top: 56px; }
    .contact-shell { margin-top: 24px; margin-bottom: 64px; gap: 40px; }
    .contact-intro h1 { font-size: 48px; letter-spacing: -2.2px; }
    .contact-lede { margin-bottom: 28px; font-size: 16px; }
    .contact-form-card { padding: 22px; }
    .contact-form-heading {
        margin-bottom: 24px;
        align-items: flex-start;
        flex-direction: column;
        gap: 8px;
    }
    .contact-field-row { grid-template-columns: 1fr; }
    .contact-submit-row { align-items: stretch; flex-direction: column; gap: 16px; }
    .contact-submit-row button { width: 100%; }
    .guide-library-shell { padding: 56px 0; gap: 40px; }
    .guide-library-intro h2 { font-size: 36px; letter-spacing: -1.4px; }
    .guide-library-summary { min-height: auto; padding: 24px; }
    .guide-library-count { font-size: 48px; letter-spacing: -3px; }
    .guide-index-shell { margin-top: 20px; }
    .guide-index-hero { margin-top: 36px; gap: 40px; }
    .guide-index-hero h1 { font-size: 46px; letter-spacing: -2px; }
    .guide-index-hero-copy > p:not(.guide-context, .guide-cta-note) {
        margin: 22px 0 26px;
        font-size: 16px;
    }
    .guide-index-hero .guide-primary { width: 100%; }
    .guide-index-library { margin-top: 72px; gap: 40px; }
    .guide-index-library-intro h2 { font-size: 36px; letter-spacing: -1.4px; }
    .guide-index-group { padding: 28px 0 48px; }
    .guide-index-group > header {
        grid-template-columns: 30px minmax(0, 1fr);
        gap: 10px;
    }
    .guide-index-group h3 { font-size: 21px; }
    .guide-index-link,
    .guide-index-group--first .guide-index-link {
        min-height: 112px;
        grid-template-columns: 30px minmax(0, 1fr) 20px;
        gap: 10px;
    }
    .guide-index-link-copy strong,
    .guide-index-group--first .guide-index-link-copy strong { font-size: 16px; }
    .guide-index-boundary {
        margin-top: 64px;
        padding: 28px 24px;
    }
    .guide-index-boundary h2 { font-size: 30px; }
    .faq-shell { padding: 64px 0 56px; gap: 40px; }
    .faq-intro h1 { font-size: 46px; letter-spacing: -2px; }
    .faq-primary { width: 100%; }
    .faq-item summary { min-height: 68px; padding-right: 44px; font-size: 16px; }
    .faq-item p { padding-right: 32px; font-size: 15px; }
    .guide-site-header,
    .guide-shell,
    .reaction-lab-shell,
    .observation-guide-shell { width: min(100% - 32px, 1180px); }
    .guide-site-header { padding: 20px 0; }
    .guide-shell { margin-top: 12px; }
    .guide-hero { margin-top: 32px; gap: 40px; }
    .guide-hero h1 { font-size: 43px; letter-spacing: -1.9px; }
    .guide-answer { margin: 22px 0 24px; font-size: 16px; }
    .guide-primary { width: 100%; }
    .guide-equation { margin-top: 64px; padding: 24px 20px; }
    .guide-equation h2 { font-size: 27px; }
    .guide-learning,
    .guide-notes { margin-top: 72px; }
    .guide-steps li { grid-template-columns: 36px minmax(0, 1fr); gap: 12px; }
    .guide-boundary { padding: 24px 20px; }
    .reaction-lab-hero { margin-top: 32px; gap: 40px; }
    .reaction-lab-hero h1 { font-size: 43px; letter-spacing: -1.9px; }
    .reaction-lab-lede { margin: 22px 0 24px; font-size: 16px; }
    .reaction-lab-output { margin-top: 64px; padding: 24px 20px; }
    .reaction-lab-output-grid, .reaction-pair-grid { grid-template-columns: 1fr; }
    .reaction-pair-grid article:nth-child(2n) { transform: none; }
    .reaction-lab-how, .reaction-lab-pairs, .reaction-lab-fit, .reaction-lab-faq, .reaction-lab-boundary, .reaction-lab-final { margin-top: 72px; }
    .reaction-lab-reading { margin-top: 80px; }
    .reaction-lab-equation-card, .reaction-lab-boundary, .reaction-lab-final { padding: 24px 20px; }
    .reaction-lab-fit-grid article { grid-template-columns: 1fr; gap: 12px; }
    .observation-guide-hero { margin-top: 32px; gap: 40px; }
    .observation-guide-hero h1 { font-size: 41px; letter-spacing: -1.8px; }
    .observation-guide-preview-frame,
    .observation-guide-preview-frame img { height: 330px; min-height: 330px; }
    .observation-guide-setup-card { right: 12px; bottom: 12px; left: 12px; padding: 16px; }
    .observation-guide-result { margin-top: 64px; padding: 24px 20px; }
    .observation-guide-equation h2 { font-size: 25px; }
    .observation-guide-observation,
    .observation-guide-ions,
    .observation-guide-study,
    .observation-guide-details,
    .observation-guide-questions,
    .observation-guide-notes,
    .observation-guide-next { margin-top: 72px; }
    .observation-vessel { height: 300px; }
    .observation-vessel::before { height: 220px; }
    .observation-guide-next { margin-bottom: 64px; }
}