/* UFC Teaching System — Shared Styles */
/* Warm dark theme matching ericbrowy.com */

:root {
    --bg-body: #0e0d0a;
    --bg-panel: rgba(23, 22, 15, 0.85);
    --bg-card: rgba(30, 28, 20, 0.9);
    --bg-code: rgba(35, 33, 22, 0.9);
    --border: #2a2720;
    --border-light: #3d3830;
    --text: #e0dbd0;
    --text-dim: #9a9484;
    --text-muted: #6b6458;
    --gold: #c4a96a;
    --gold-dim: #a08a50;
    --blue: #b8a878;
    --blue-dim: #9a8a60;
    --green: #7dba6a;
    --red: #c47a6a;
    --purple: #b8a070;
    --font-body: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    --max-width: 820px;
    --nav-height: 52px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    background: var(--bg-body);
    color: var(--text);
    font-family: var(--font-body);
    font-size: 17px;
    line-height: 1.7;
    min-height: 100vh;
}

/* ── Navigation ── */
nav.top-nav {
    position: sticky; top: 0; z-index: 100;
    height: var(--nav-height);
    background: rgba(14, 13, 10, 0.95);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    display: flex; align-items: center;
    padding: 0 20px; gap: 16px;
}

nav.top-nav .brand {
    font-size: 15px; font-weight: 700;
    color: var(--gold);
    text-decoration: none;
    white-space: nowrap;
}

nav.top-nav .chapter-title {
    font-size: 14px; color: var(--text-dim);
    overflow: hidden; text-overflow: ellipsis;
    white-space: nowrap; flex: 1;
}

nav.top-nav .nav-links {
    display: flex; gap: 8px; align-items: center;
}

nav.top-nav .nav-btn {
    background: var(--bg-card);
    border: 1px solid var(--border);
    color: var(--text-dim);
    padding: 5px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 13px;
    text-decoration: none;
    transition: all 0.15s;
}

nav.top-nav .nav-btn:hover {
    background: var(--bg-code);
    color: var(--text);
    border-color: var(--border-light);
}

/* ── Level Switcher ── */
.level-switcher {
    display: flex; gap: 4px;
    background: var(--bg-panel);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 3px;
}

.level-btn {
    background: none; border: none;
    color: var(--text-muted);
    padding: 4px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 12px;
    font-weight: 600;
    transition: all 0.15s;
}

.level-btn:hover { color: var(--text-dim); }

.level-btn.active {
    background: var(--bg-code);
    color: var(--gold);
}

/* ── Content ── */
main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 40px 24px 80px;
}

h1 {
    font-size: 2.2em; color: var(--gold);
    margin-bottom: 8px; line-height: 1.2;
}

h1 .chapter-num {
    font-size: 0.5em; color: var(--text-muted);
    display: block; margin-bottom: 4px;
    font-weight: 400; letter-spacing: 2px;
    text-transform: uppercase;
}

h2 {
    font-size: 1.5em; color: var(--gold);
    margin: 48px 0 16px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border);
}

h3 {
    font-size: 1.15em; color: var(--text);
    margin: 32px 0 12px;
}

p { margin-bottom: 16px; }

a { color: var(--gold); text-decoration: none; }
a:hover { text-decoration: underline; color: var(--gold); }

strong { color: var(--gold); font-weight: 600; }

em { color: var(--text); font-style: italic; }

code {
    font-family: var(--font-mono);
    background: var(--bg-code);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.9em;
    color: var(--gold-dim);
}

/* ── Derivation blocks ── */
.derivation {
    background: var(--bg-panel);
    border: 1px solid var(--border);
    border-left: 3px solid var(--gold);
    border-radius: 8px;
    padding: 24px;
    margin: 24px 0;
}

.derivation .step {
    margin: 16px 0;
}

.derivation .step-label {
    font-size: 12px;
    font-weight: 700;
    color: var(--gold-dim);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 4px;
}

.derivation .annotation {
    font-size: 0.9em;
    color: var(--text-dim);
    font-style: italic;
    margin-top: 4px;
}

/* ── Key result callout ── */
.result-box {
    background: linear-gradient(135deg, rgba(196,169,106,0.08), rgba(160,138,80,0.05));
    border: 2px solid var(--gold);
    border-radius: 12px;
    padding: 24px;
    margin: 32px 0;
    text-align: center;
}

.result-box .result-label {
    font-size: 12px; font-weight: 700;
    color: var(--gold-dim);
    text-transform: uppercase;
    letter-spacing: 2px;
    margin-bottom: 8px;
}

.result-box .katex-display { margin: 12px 0; }

/* ── Visualization containers ── */
.viz-container {
    background: var(--bg-panel);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 16px;
    margin: 24px 0;
}

.viz-container canvas {
    width: 100%;
    border-radius: 8px;
    display: block;
}

.viz-controls {
    display: flex; flex-wrap: wrap;
    gap: 16px; padding: 12px 0 4px;
    align-items: center;
}

.viz-controls label {
    font-size: 13px; color: var(--text-dim);
    display: flex; align-items: center; gap: 8px;
}

.viz-controls input[type="range"] {
    accent-color: var(--gold);
    width: 120px;
}

.viz-controls .value {
    font-family: var(--font-mono);
    font-size: 13px;
    color: var(--gold);
    min-width: 50px;
}

/* ── Foundation links ── */
.foundation-link {
    display: inline-flex; align-items: center; gap: 4px;
    background: var(--bg-code);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 2px 10px;
    font-size: 0.85em;
    color: var(--gold-dim);
    text-decoration: none;
    transition: all 0.15s;
}

.foundation-link:hover {
    border-color: var(--gold-dim);
    text-decoration: none;
}

.foundation-link::before { content: '\01F4D6 '; font-size: 0.9em; }

/* ── Level-gated content ── */
main > [data-level] { display: none; }
body[data-active-level="intuitive"] main > [data-level="intuitive"],
body[data-active-level="conceptual"] main > [data-level="conceptual"],
body[data-active-level="derivation"] main > [data-level="derivation"],
body[data-active-level="expert"] main > [data-level="expert"] { display: block; }

/* Show lower levels too (cascading) */
body[data-active-level="conceptual"] main > [data-level="intuitive"] { display: block; }
body[data-active-level="derivation"] main > [data-level="intuitive"],
body[data-active-level="derivation"] main > [data-level="conceptual"] { display: block; }
body[data-active-level="expert"] main > [data-level="intuitive"],
body[data-active-level="expert"] main > [data-level="conceptual"],
body[data-active-level="expert"] main > [data-level="derivation"] { display: block; }

/* Level indicators */
main > [data-level]::before {
    font-size: 10px; font-weight: 700;
    text-transform: uppercase; letter-spacing: 1px;
    padding: 2px 8px; border-radius: 4px;
    display: inline-block; margin-bottom: 8px;
}
main > [data-level="intuitive"]::before { content: ''; }
main > [data-level="conceptual"]::before {
    content: 'Conceptual';
    background: rgba(196,169,106,0.1); color: var(--gold-dim);
}
main > [data-level="derivation"]::before {
    content: 'Derivation';
    background: rgba(196,169,106,0.15); color: var(--gold);
}
main > [data-level="expert"]::before {
    content: 'Expert';
    background: rgba(160,138,80,0.15); color: var(--gold-dim);
}

/* ── Chapter navigation footer ── */
.chapter-nav-footer {
    display: flex; justify-content: space-between;
    margin-top: 64px; padding-top: 24px;
    border-top: 1px solid var(--border);
}

.chapter-nav-footer a {
    display: flex; flex-direction: column;
    padding: 12px 16px;
    background: var(--bg-panel);
    border: 1px solid var(--border);
    border-radius: 8px;
    text-decoration: none;
    transition: all 0.15s;
    max-width: 45%;
}

.chapter-nav-footer a:hover {
    border-color: var(--gold);
    background: var(--bg-card);
}

.chapter-nav-footer a .dir {
    font-size: 11px; color: var(--text-muted);
    text-transform: uppercase; letter-spacing: 1px;
}

.chapter-nav-footer a .title {
    font-size: 15px; color: var(--gold);
    margin-top: 2px;
}

/* ── KaTeX overrides ── */
.katex-display { margin: 20px 0; overflow-x: auto; overflow-y: hidden; }
.katex { color: var(--text); }

/* ── Index page specifics ── */
.chapter-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    margin: 24px 0;
}

.chapter-card {
    display: flex; align-items: baseline; gap: 16px;
    padding: 16px 20px;
    background: var(--bg-panel);
    border: 1px solid var(--border);
    border-radius: 10px;
    text-decoration: none;
    transition: all 0.2s;
}

.chapter-card:hover {
    border-color: var(--gold-dim);
    background: var(--bg-card);
    text-decoration: none;
    transform: translateX(4px);
}

.chapter-card .ch-num {
    font-size: 13px; font-weight: 700;
    color: var(--text-muted); font-family: var(--font-mono);
    min-width: 28px;
}

.chapter-card .ch-title {
    font-size: 16px; color: var(--gold);
    font-weight: 600;
}

.chapter-card .ch-desc {
    font-size: 14px; color: var(--text-dim);
    margin-top: 2px;
}

/* ── Subtitle / lede ── */
.lede {
    font-size: 1.15em;
    color: var(--text-dim);
    margin-bottom: 32px;
    line-height: 1.6;
}

/* ── Inline level switcher (always visible, inside main) ── */
.inline-level-switcher {
    display: flex; gap: 8px; flex-wrap: wrap;
    margin: -8px 0 32px;
}

.inline-level-switcher .level-btn {
    background: var(--bg-panel);
    border: 1px solid var(--border);
    color: var(--text-muted);
    padding: 8px 18px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 600;
    transition: all 0.15s;
}

.inline-level-switcher .level-btn:hover {
    color: var(--text-dim);
    background: var(--bg-code);
    border-color: var(--border-light);
}

.inline-level-switcher .level-btn.active {
    background: var(--bg-code);
    color: var(--gold);
    border-color: var(--gold-dim);
    box-shadow: 0 0 10px rgba(196,169,106,0.15);
}

/* ── Responsive ── */
@media (max-width: 640px) {
    body { font-size: 15px; }
    main { padding: 24px 16px 60px; }
    h1 { font-size: 1.7em; }
    nav.top-nav { padding: 0 12px; gap: 8px; }
    nav.top-nav .level-switcher { display: none; }
    .viz-controls { flex-direction: column; gap: 8px; }
    .chapter-nav-footer { flex-direction: column; gap: 12px; }
    .chapter-nav-footer a { max-width: 100%; }
}