/* ==========================================================================
   Flash Tutorial — visual system
   --------------------------------------------------------------------------
   Clean, Apple/Google-inspired: generous whitespace, a confident type scale,
   soft tonal elevation instead of hairline-everywhere, white cards on a calm
   grey app surface (light) / deep neutral surfaces (dark). One brand accent —
   Flash amber — graded per surface so small text always clears ~4.5:1.
   Syntax highlighting (Monaco) stays One Dark / One Light verbatim.
   ========================================================================== */
:root {
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-display: 'Orbitron', var(--font-sans); /* wordmark only */
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Softer, larger radii read calmer than tight corners */
    --radius-s: 10px;   /* small controls */
    --radius-m: 14px;   /* cards, callouts, code blocks */
    --radius-l: 20px;   /* large panels */
    --radius-pill: 999px;

    /* Spacing scale */
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-5: 24px;
    --space-6: 32px;
    --space-7: 48px;

    --transition-fast: 0.15s ease;
    --transition-normal: 0.28s cubic-bezier(0.32, 0.72, 0, 1); /* Apple-style ease */
    --header-h: 64px;
}

.dark-theme {
    /* Surfaces — deep neutral, a touch warmer than pure black */
    --bg-app: #17191e;
    --bg-panel: #1f2229;
    --bg-panel-hover: #262a32;
    --bg-header: rgba(23, 25, 30, 0.72);
    --bg-elevated: #21252b;
    --border-color: #2b2f37;
    --border-subtle: #23272e;

    /* Text */
    --ink: #f5f5f7;            /* wordmark neutral */
    --text-primary: #e6e8ec;
    --text-secondary: #b3b8c2;
    --text-muted: #7d828d;

    /* Brand accent (amber) — matches the dark logo "lash" (#FBBF24) */
    --accent: #fbbf24;          /* text & icons on dark */
    --accent-fill: #fbbf24;     /* filled controls, wordmark "lash" */
    --accent-fill-hover: #fcd34d;
    --accent-ink: #1a1205;      /* text on an amber fill */
    --accent-glow: rgba(251, 191, 36, 0.14);
    --accent-glow-strong: rgba(251, 191, 36, 0.22);

    /* Semantic states */
    --info: #61afef;    --info-bg: rgba(97, 175, 239, 0.12);
    --success: #98c379; --success-bg: rgba(152, 195, 121, 0.12);
    --error: #e06c75;   --error-bg: rgba(224, 108, 117, 0.12);
    --warning: #d19a66; --warning-bg: rgba(209, 154, 102, 0.12);

    /* Editor & terminal surfaces — One Dark verbatim to match Monaco */
    --bg-editor: #282c34;
    --bg-terminal: #16181d;

    /* Soft elevation (subtle on dark; pairs with a faint border) */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.30);
    --shadow-md: 0 6px 20px rgba(0, 0, 0, 0.36);
    --shadow-lg: 0 20px 48px rgba(0, 0, 0, 0.50);
}

.light-theme {
    /* Surfaces — Apple-style calm grey app, white cards */
    --bg-app: #f5f5f7;
    --bg-panel: #ffffff;
    --bg-panel-hover: #f0f0f3;
    --bg-header: rgba(255, 255, 255, 0.75);
    --bg-elevated: #ffffff;
    --border-color: #e4e4ea;
    --border-subtle: #ececf1;

    /* Text */
    --ink: #1d1d1f;
    --text-primary: #1d1d1f;
    --text-secondary: #515154;
    --text-muted: #86868b;

    /* Brand accent (amber, darkened for small text on light) */
    --accent: #b45309;
    --accent-fill: #f59e0b;
    --accent-fill-hover: #d97706;
    --accent-ink: #2a1d04;
    --accent-glow: rgba(245, 158, 11, 0.12);
    --accent-glow-strong: rgba(245, 158, 11, 0.18);

    /* Semantic states */
    --info: #2563eb;    --info-bg: rgba(37, 99, 235, 0.08);
    --success: #16a34a; --success-bg: rgba(22, 163, 74, 0.08);
    --error: #dc2626;   --error-bg: rgba(220, 38, 38, 0.08);
    --warning: #c18401; --warning-bg: rgba(193, 132, 1, 0.10);

    /* Editor & terminal surfaces — One Light verbatim to match Monaco */
    --bg-editor: #fafafa;
    --bg-terminal: #f5f5f7;

    /* Soft elevation — layered, low-opacity (Apple/Google) */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04), 0 1px 3px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.06), 0 2px 6px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 16px 40px rgba(0, 0, 0, 0.10), 0 4px 12px rgba(0, 0, 0, 0.06);
}

/* ==========================================================================
   Base Elements & Reset
   ========================================================================== */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html { -webkit-text-size-adjust: 100%; }

body {
    font-family: var(--font-sans);
    background-color: var(--bg-app);
    color: var(--text-primary);
    line-height: 1.6;
    overflow: hidden;
    height: 100vh;
    height: 100dvh; /* mobile: track the real viewport when the URL bar collapses */
    display: flex;
    flex-direction: column;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

a {
    color: var(--accent);
    text-decoration: none;
    text-underline-offset: 2px;
    transition: color var(--transition-fast);
}
a:hover {
    color: var(--accent-fill-hover);
    text-decoration: underline;
}

button {
    cursor: pointer;
    font-family: var(--font-sans);
    border: none;
    background: none;
    color: inherit;
}

:focus-visible {
    outline: 2px solid var(--accent-fill);
    outline-offset: 2px;
    border-radius: var(--radius-s);
}

::selection {
    background-color: var(--accent-glow-strong);
    color: var(--text-primary);
}

/* Thin, quiet scrollbars */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border: 3px solid transparent;
    background-clip: padding-box;
    border-radius: var(--radius-pill);
}
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); background-clip: padding-box; }

/* ==========================================================================
   Header — clean nav bar, frosted glass over the app surface
   ========================================================================== */
.app-header {
    height: var(--header-h);
    background-color: var(--bg-header);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 24px;
    z-index: 30;
    flex-shrink: 0;
    transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.header-logo-section {
    display: flex;
    align-items: center;
    gap: 14px;
}

/* Brand wordmark: bold neutral "F" + regular amber "lash" (Orbitron) */
.wordmark {
    font-family: var(--font-display);
    font-size: 19px;
    font-weight: 400;
    letter-spacing: 0.02em;
    line-height: 1;
}
.wordmark-f { font-weight: 700; color: var(--ink); }
.wordmark-lash { color: var(--accent-fill); }

.sub-badge {
    font-size: 11px;
    font-weight: 600;
    background-color: var(--accent-glow);
    color: var(--accent);
    padding: 4px 10px;
    border-radius: var(--radius-pill);
    text-transform: uppercase;
    letter-spacing: 0.07em;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
}

.github-btn {
    display: flex;
    align-items: center;
    gap: 7px;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-primary);
    background-color: var(--bg-panel);
    border: 1px solid var(--border-color);
    padding: 7px 15px;
    border-radius: var(--radius-pill);
    transition: background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.github-btn:hover {
    background-color: var(--bg-panel-hover);
    text-decoration: none;
    color: var(--text-primary);
    box-shadow: var(--shadow-sm);
}
.github-btn i { width: 15px; height: 15px; }

.theme-toggle-btn, .layout-toggle-btn, .sidebar-toggle-btn {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-s);
    border: 1px solid transparent;
    background-color: transparent;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-fast), color var(--transition-fast);
}
.theme-toggle-btn:hover, .layout-toggle-btn:hover, .sidebar-toggle-btn:hover {
    background-color: var(--bg-panel-hover);
    color: var(--accent);
}
.theme-toggle-btn i, .layout-toggle-btn i, .sidebar-toggle-btn i { width: 18px; height: 18px; }

/* Drawer toggle exists only on narrow screens (see media queries) */
.sidebar-toggle-btn { display: none; flex-shrink: 0; }

/* Theme button shows only the icon for the current mode (auto/light/dark). */
.auto-icon, .light-icon, .dark-icon { display: none; }
.theme-toggle-btn[data-mode="auto"] .auto-icon { display: block; }
.theme-toggle-btn[data-mode="light"] .light-icon { display: block; }
.theme-toggle-btn[data-mode="dark"] .dark-icon { display: block; }

/* ==========================================================================
   App Layout
   ========================================================================== */
.app-layout {
    display: flex;
    flex: 1;
    overflow: hidden;
    position: relative;
}

/* Sidebar Navigation */
.app-sidebar {
    width: 280px;
    background-color: var(--bg-app);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
    transition: background-color var(--transition-normal);
}

/* Dim layer behind the off-canvas drawer; activated on narrow screens */
.sidebar-backdrop {
    display: none;
    position: fixed;
    top: var(--header-h);
    left: 0; right: 0; bottom: 0;
    background-color: rgba(0, 0, 0, 0.40);
    -webkit-backdrop-filter: blur(2px);
    backdrop-filter: blur(2px);
    z-index: 40;
}
.sidebar-backdrop.visible { display: block; }

.sidebar-header { padding: 24px 28px 10px; }
.sidebar-header h3 {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.09em;
    color: var(--text-muted);
}

.sidebar-nav {
    flex: 1;
    overflow-y: auto;
    padding: 4px 16px 20px;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.nav-item {
    display: flex;
    align-items: center;
    padding: 10px 14px;
    border-radius: var(--radius-s);
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    line-height: 1.3;
    text-align: left;
    transition: background-color var(--transition-fast), color var(--transition-fast);
}
.nav-item:hover {
    background-color: var(--bg-panel-hover);
    color: var(--text-primary);
}
.nav-item.active {
    background-color: var(--accent-glow);
    color: var(--accent);
    font-weight: 600;
}

.nav-loading {
    padding: 20px;
    text-align: center;
    color: var(--text-muted);
    font-size: 13px;
}

/* Workspace Pane (Split Screen) */
.workspace-pane {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0;
    overflow: hidden;
    padding: 16px 16px 16px 0;
    transition: grid-template-columns var(--transition-normal);
}

/* Workspace Layout Modes */
.workspace-pane.reader-only { grid-template-columns: 1fr 0px; }
.workspace-pane.editor-only { grid-template-columns: 0px 1fr; }

/* ==========================================================================
   Content Reader Panel (Left)
   ========================================================================== */
.content-panel {
    display: flex;
    flex-direction: column;
    background-color: var(--bg-app);
    overflow: hidden;
    transition: background-color var(--transition-normal);
}

.content-body {
    flex: 1;
    overflow-y: auto;
    padding: 56px 56px 64px;
    font-size: 16px;
    color: var(--text-primary);
    scroll-behavior: smooth;
}

/* Comfortable reading measure. Plain block flow left-aligns by default (the
   centring auto-margins are gone), and lets the panel scroll normally —
   a flex column here squishes tall code blocks instead of stacking them. */
.content-body > * {
    max-width: 820px;
}

/* Markdown rendering — hierarchy through type scale and space, no boxes */
.content-body h1, .content-body h2, .content-body h3 {
    color: var(--text-primary);
    font-weight: 700;
    letter-spacing: -0.022em;
}
.content-body h1 { font-size: 36px; line-height: 1.1; margin: 0 0 12px; }
.content-body h2 { font-size: 25px; line-height: 1.2; margin: 56px 0 16px; }
.content-body h3 { font-size: 19px; line-height: 1.3; margin: 36px 0 12px; letter-spacing: -0.015em; }

.content-body p { margin: 0 0 18px; color: var(--text-secondary); line-height: 1.75; }
.content-body ul, .content-body ol { margin: 0 0 20px; padding-left: 22px; color: var(--text-secondary); }
.content-body li { margin-bottom: 8px; line-height: 1.7; }
.content-body li::marker { color: var(--text-muted); }
.content-body strong { color: var(--text-primary); font-weight: 600; }
.content-body hr { border: none; border-top: 1px solid var(--border-subtle); margin: 40px 0; }

/* Plain blockquotes */
.content-body blockquote {
    margin: 24px 0;
    padding: 14px 22px;
    border-left: 3px solid var(--accent-fill);
    background-color: var(--bg-panel);
    border-radius: var(--radius-m);
    box-shadow: var(--shadow-sm);
}
.content-body blockquote p { margin-bottom: 0; color: var(--text-primary); font-weight: 500; }

/* Callout alerts (GitHub semantics: note=blue, tip=green, warning=amber) */
.callout {
    margin: 24px 0;
    padding: 16px 20px;
    border-radius: var(--radius-m);
    border: 1px solid var(--border-subtle);
    border-left: 3px solid var(--info);
    background-color: var(--bg-panel);
    box-shadow: var(--shadow-sm);
}
.callout-title {
    font-weight: 600;
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 8px;
}
.callout p { margin-bottom: 0; }
.callout-note { border-left-color: var(--info); }
.callout-note .callout-title { color: var(--info); }
.callout-tip { border-left-color: var(--success); }
.callout-tip .callout-title { color: var(--success); }
.callout-warning { border-left-color: var(--warning); }
.callout-warning .callout-title { color: var(--warning); }

/* Code & tables */
.content-body pre {
    background-color: var(--bg-panel);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-m);
    padding: 18px 20px;
    margin: 24px 0;
    overflow-x: auto;
    box-shadow: var(--shadow-sm);
}
.content-body code {
    font-family: var(--font-mono);
    font-size: 13.5px;
    background-color: var(--bg-panel-hover);
    border: 1px solid var(--border-subtle);
    padding: 1px 6px;
    border-radius: 6px;
    color: var(--text-primary);
}
.content-body pre code {
    background-color: transparent;
    border: none;
    padding: 0;
    border-radius: 0;
    font-size: 13.5px;
    line-height: 1.6;
}

.content-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 24px 0;
    font-size: 14px;
}
.content-body th, .content-body td {
    text-align: left;
    padding: 10px 14px;
    border-bottom: 1px solid var(--border-subtle);
}
.content-body th { color: var(--text-primary); font-weight: 600; }
.content-body td { color: var(--text-secondary); }

/* Runnable example cards */
.example-card {
    background-color: var(--bg-panel);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-m);
    margin: 28px 0;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: box-shadow var(--transition-fast);
}
.example-card:hover { box-shadow: var(--shadow-md); }
.example-header {
    padding: 12px 18px;
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.example-title {
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
}
.example-card pre {
    border: none;
    border-radius: 0;
    margin: 0;
    max-width: none;
    box-shadow: none;
    background-color: transparent;
}
.load-example-btn {
    font-size: 12px;
    font-weight: 600;
    background-color: var(--accent-glow);
    color: var(--accent);
    padding: 5px 13px;
    border-radius: var(--radius-pill);
    display: flex;
    align-items: center;
    gap: 5px;
    transition: background-color var(--transition-fast), color var(--transition-fast);
}
.load-example-btn:hover {
    background-color: var(--accent-fill);
    color: var(--accent-ink);
}

/* Loading state */
.content-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    max-width: none;
    min-height: 60vh;
    color: var(--text-secondary);
    gap: 16px;
}
.spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--border-color);
    border-top-color: var(--accent-fill);
    border-radius: 50%;
    animation: spin 1s infinite linear;
}

/* Chapter prev/next */
.content-nav-buttons {
    padding: 16px 40px;
    display: flex;
    justify-content: space-between;
    gap: 12px;
}
.nav-btn {
    display: flex;
    align-items: center;
    gap: 7px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-primary);
    background-color: var(--bg-panel);
    border: 1px solid var(--border-color);
    padding: 9px 18px;
    border-radius: var(--radius-pill);
    transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast), box-shadow var(--transition-fast);
}
.nav-btn:hover:not(:disabled) {
    background-color: var(--bg-panel);
    border-color: var(--accent-fill);
    color: var(--accent);
    box-shadow: var(--shadow-sm);
}
.nav-btn:disabled { opacity: 0.4; cursor: not-allowed; }
.nav-btn i { width: 16px; height: 16px; }

/* ==========================================================================
   Playground Panel (Right) — a floating card
   ========================================================================== */
.playground-panel {
    display: flex;
    flex-direction: column;
    overflow: hidden;
    background-color: var(--bg-panel);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-l);
    box-shadow: var(--shadow-md);
}

.playground-header {
    height: 52px;
    background-color: var(--bg-panel);
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 14px;
    flex-shrink: 0;
}

.tab-selectors {
    display: flex;
    gap: 4px;
    align-items: center;
    background-color: var(--bg-app);
    padding: 4px;
    border-radius: var(--radius-pill);
}
.tab-btn {
    padding: 6px 14px;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-pill);
    display: flex;
    align-items: center;
    gap: 6px;
    transition: color var(--transition-fast), background-color var(--transition-fast), box-shadow var(--transition-fast);
}
.tab-btn:hover { color: var(--text-primary); }
.tab-btn.active {
    color: var(--accent);
    background-color: var(--bg-panel);
    box-shadow: var(--shadow-sm);
    font-weight: 600;
}
.tab-btn i { width: 14px; height: 14px; }

.playground-actions { display: flex; align-items: center; }

.action-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 13px;
    font-weight: 600;
    padding: 8px 18px;
    border-radius: var(--radius-pill);
    transition: background-color var(--transition-fast), transform var(--transition-fast), box-shadow var(--transition-fast);
}
.action-btn:active { transform: scale(0.97); }
.action-btn.primary {
    background-color: var(--accent-fill);
    color: var(--accent-ink);
    box-shadow: var(--shadow-sm);
}
.action-btn.primary:hover {
    background-color: var(--accent-fill-hover);
    box-shadow: var(--shadow-md);
}
.action-btn i { width: 14px; height: 14px; }

.playground-body {
    flex: 1;
    overflow: hidden;
    position: relative;
}

.tab-content {
    display: none;
    width: 100%;
    height: 100%;
    overflow: hidden;
}
.tab-content.active { display: block; }

#editor-container, #output-container {
    width: 100%;
    height: 100%;
    background-color: var(--bg-editor);
}

/* ==========================================================================
   Terminal Drawer
   ========================================================================== */
.playground-terminal {
    height: 168px;
    background-color: var(--bg-terminal);
    border-top: 1px solid var(--border-subtle);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    flex-shrink: 0;
    transition: height var(--transition-normal);
}

.terminal-header {
    height: 40px;
    flex-shrink: 0;
    padding: 0 16px;
    background-color: var(--bg-terminal);
    display: flex;
    justify-content: space-between;
    align-items: center;
    user-select: none;
    cursor: pointer; /* tap to collapse/expand the drawer */
}

.playground-terminal.collapsed { height: 40px; }

/* Collapse chevron in the terminal header */
.terminal-chevron {
    width: 16px;
    height: 16px;
    color: var(--text-muted);
    transition: transform var(--transition-fast);
}
.playground-terminal.collapsed .terminal-chevron { transform: rotate(180deg); }

.terminal-title {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 7px;
}
.terminal-title i { width: 14px; height: 14px; }

.terminal-controls {
    display: flex;
    align-items: center;
    gap: 12px;
}

.status-indicator {
    font-size: 11px;
    font-weight: 600;
    padding: 3px 10px;
    border-radius: var(--radius-pill);
    letter-spacing: 0.02em;
}
.status-indicator.idle { background-color: var(--bg-panel-hover); color: var(--text-secondary); }
.status-indicator.transpiling { background-color: var(--accent-glow); color: var(--accent); }
.status-indicator.success { background-color: var(--success-bg); color: var(--success); }
.status-indicator.error { background-color: var(--error-bg); color: var(--error); }

.control-btn {
    color: var(--text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--transition-fast);
}
.control-btn:hover { color: var(--error); }
.control-btn i { width: 15px; height: 15px; }

.terminal-output {
    flex: 1;
    padding: 14px 16px;
    overflow-y: auto;
    font-family: var(--font-mono);
    font-size: 12.5px;
    color: var(--text-secondary);
    white-space: pre-wrap;
    line-height: 1.55;
}
.terminal-output.log-error { color: var(--error); }
.terminal-output.log-success { color: var(--success); }
.terminal-output.log-warning { color: var(--warning); }

/* ==========================================================================
   Animations — functional only, nothing decorative
   ========================================================================== */
@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* ==========================================================================
   Responsive (Medium Screens)
   --------------------------------------------------------------------------
   ≤992px: the chapters sidebar becomes an off-canvas drawer (hamburger in
   the header), and the reader/playground panes stack vertically. The app
   keeps its fixed-viewport layout — 100dvh on <body> handles mobile URL bars.
   ========================================================================== */
@media (max-width: 992px) {
    .sidebar-toggle-btn { display: flex; }

    .app-sidebar {
        position: fixed;
        top: var(--header-h);
        bottom: 0;
        left: 0;
        width: 300px;
        max-width: 85vw;
        z-index: 50;
        background-color: var(--bg-panel);
        border-right: 1px solid var(--border-subtle);
        box-shadow: var(--shadow-lg);
        transform: translateX(-110%);
        transition: transform var(--transition-normal);
    }
    .app-sidebar.open { transform: translateX(0); }

    .workspace-pane {
        grid-template-columns: 1fr;
        grid-template-rows: 1fr 1fr;
        gap: 12px;
        padding: 12px;
    }
    .workspace-pane.reader-only {
        grid-template-columns: 1fr;
        grid-template-rows: 1fr 0px;
    }
    .workspace-pane.editor-only {
        grid-template-columns: 1fr;
        grid-template-rows: 0px 1fr;
    }
}

@media (max-width: 600px) {
    body { --header-h: 56px; }
    .app-header { padding: 0 14px; height: 56px; }
    .header-actions { gap: 4px; }
    .github-label { display: none; } /* icon-only GitHub button saves header width */
    .github-btn { padding: 7px 10px; }

    .content-body { padding: 32px 20px 44px; font-size: 15px; }
    .content-body h1 { font-size: 29px; }
    .content-body h2 { font-size: 22px; margin-top: 40px; }
    .content-nav-buttons { padding: 12px 20px; }

    .workspace-pane { padding: 10px; gap: 10px; }
    .playground-header { padding: 0 10px; height: 48px; }
    .tab-btn { padding: 6px 11px; }
    .action-btn { padding: 7px 13px; }

    /* Smaller default drawer; users can collapse it by tapping its header */
    .playground-terminal { height: 140px; }
}