:root {
    --bg: #0b0b0c;
    --surface: #131315;
    --text-main: #f4f4f6;
    --text-muted: #8a8a93;
    --accent: #6366f1;
    --border: #222226;

    /* Fibonacci Spacing & Layout System */
    --f1: 8px;
    --f2: 13px;
    --f3: 21px;
    --f5: 34px;
    --f8: 55px;
    --f13: 89px;
    --f21: 144px;
}
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    background-color: var(--bg);
    color: var(--text-main);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}
/* Pure Geometric Fibonacci Grid Layout */
.fibonacci-grid {
    display: grid;
    grid-template-columns: minmax(0, var(--f21)) minmax(0, 1fr);
    gap: var(--f5);
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
    padding: var(--f8) var(--f5);
    flex: 1;
}
/* Sidebar Pane (Fibonacci Width 1: 144px proportion) */
.panel-alpha {
    display: flex;
    flex-direction: column;
    gap: var(--f8);
}
.logo-mark {
    font-size: var(--f3);
    font-weight: 700;
    letter-spacing: -0.05em;
    color: var(--text-main);
    text-decoration: none;
    display: block;
}
.nav-links {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--f2);
}
.nav-links a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    transition: color 0.2s ease;
}
.nav-links a:hover {
    color: var(--text-main);
}
/* Main Display Pane (Fibonacci Width 2: Expanding Proportions) */
.panel-beta {
    display: flex;
    flex-direction: column;
    gap: var(--f13);
}
.hero-section h1 {
    font-size: var(--f5);
    font-weight: 600;
    letter-spacing: -0.03em;
    line-height: 1.2;
    max-width: 600px;
    margin-bottom: var(--f3);
    text-wrap: balance;
}
.hero-section p {
    color: var(--text-muted);
    font-size: 16px;
    max-width: 520px;
}
/* Modular Category Grid mirroring Golden Proportions */
.brackets-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--f3);
}
.bracket-card {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: var(--f5);
    border-radius: 4px;
    display: flex;
    flex-direction: column;
    gap: var(--f2);
}
.bracket-card h3 {
    font-size: 18px;
    font-weight: 600;
    letter-spacing: -0.01em;
}
.bracket-card p {
    color: var(--text-muted);
    font-size: 14px;
    line-height: 1.6;
}
.meta-spec {
    font-family: monospace;
    font-size: 12px;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: auto;
    padding-top: var(--f2);
}

/* ── Section shared styles ── */
.content-section {
    display: flex;
    flex-direction: column;
    gap: var(--f5);
}
.section-heading {
    font-size: 22px;
    font-weight: 600;
    letter-spacing: -0.02em;
    padding-bottom: var(--f2);
    border-bottom: 1px solid var(--border);
}
.section-lead {
    color: var(--text-muted);
    font-size: 15px;
    max-width: 560px;
}
code {
    font-family: "SF Mono", "Fira Code", "Cascadia Mono", Menlo, monospace;
    font-size: 0.85em;
    color: var(--accent);
    background: color-mix(in srgb, var(--accent) 10%, transparent);
    padding: 1px 5px;
    border-radius: 3px;
}

/* ── Constraints Table ── */
.constraints-table {
    border: 1px solid var(--border);
    border-radius: 4px;
    overflow: hidden;
}
.constraints-header,
.constraints-row {
    display: grid;
    grid-template-columns: 160px 1fr 1fr;
    gap: 0;
}
.constraints-header {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
}
.constraints-header span {
    padding: var(--f2) var(--f3);
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
}
.constraints-header span:not(:last-child),
.constraints-row span:not(:last-child) {
    border-right: 1px solid var(--border);
}
.constraints-row {
    border-bottom: 1px solid var(--border);
    font-size: 14px;
}
.constraints-row:last-child {
    border-bottom: none;
}
.constraints-row span {
    padding: var(--f2) var(--f3);
    color: var(--text-muted);
    line-height: 1.5;
}
.constraint-label {
    color: var(--text-main) !important;
    font-weight: 500;
    font-size: 13px !important;
}

/* ── Requirements List ── */
.requirements-list {
    display: flex;
    flex-direction: column;
    gap: 0;
    border: 1px solid var(--border);
    border-radius: 4px;
    overflow: hidden;
}
.requirement-item {
    display: flex;
    align-items: flex-start;
    gap: var(--f5);
    padding: var(--f5);
    border-bottom: 1px solid var(--border);
}
.requirement-item:last-child {
    border-bottom: none;
}
.requirement-index {
    font-family: "SF Mono", "Fira Code", "Cascadia Mono", Menlo, monospace;
    font-size: 11px;
    color: var(--accent);
    letter-spacing: 0.04em;
    padding-top: 2px;
    min-width: 20px;
    flex-shrink: 0;
}
.requirement-item h4 {
    font-size: 15px;
    font-weight: 600;
    letter-spacing: -0.01em;
    margin-bottom: var(--f1);
    font-family: "SF Mono", "Fira Code", "Cascadia Mono", Menlo, monospace;
}
.requirement-item p {
    color: var(--text-muted);
    font-size: 14px;
    line-height: 1.6;
}

/* ── Code Block ── */
.code-block {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: var(--f5);
    overflow-x: auto;
    font-family: "SF Mono", "Fira Code", "Cascadia Mono", Menlo, monospace;
    font-size: 13px;
    line-height: 1.7;
    color: var(--text-muted);
}
.code-block code {
    background: none;
    padding: 0;
    font-size: 13px;
    color: inherit;
    border-radius: 0;
}
.code-block .kw  { color: #818cf8; }
.code-block .cls { color: #a5b4fc; }
.code-block .fn  { color: #c4b5fd; }
.code-block .str { color: #6ee7b7; }
.code-block .cm  { color: #4b5563; }
.code-block .num { color: #f9a8d4; }

/* ── Rules Grid ── */
.rules-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--f3);
}
.rule-item {
    display: flex;
    flex-direction: column;
    gap: var(--f2);
    padding: var(--f5);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
}
.rule-tag {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--accent);
}
.rule-item p {
    color: var(--text-muted);
    font-size: 14px;
    line-height: 1.6;
}

/* ── CTA Section ── */
.cta-section {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--f5);
    padding: var(--f5);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 4px;
    flex-wrap: wrap;
}
.cta-body h2 {
    font-size: 20px;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: var(--f1);
}
.cta-body p {
    color: var(--text-muted);
    font-size: 14px;
    max-width: 400px;
}
.cta-actions {
    display: flex;
    gap: var(--f2);
    flex-shrink: 0;
}
.btn-primary {
    display: inline-block;
    padding: 10px var(--f3);
    background: var(--accent);
    color: #fff;
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    border-radius: 4px;
    transition: opacity 0.2s ease;
    white-space: nowrap;
}
.btn-primary:hover {
    opacity: 0.85;
}
.btn-ghost {
    display: inline-block;
    padding: 10px var(--f3);
    background: transparent;
    color: var(--text-muted);
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    border: 1px solid var(--border);
    border-radius: 4px;
    transition: color 0.2s ease, border-color 0.2s ease;
    white-space: nowrap;
}
.btn-ghost:hover {
    color: var(--text-main);
    border-color: #3a3a40;
}

footer {
    border-top: 1px solid var(--border);
    padding: var(--f5) 0;
    margin-top: var(--f13);
}
.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--f5);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 12px;
    color: var(--text-muted);
}
/* Clean responsiveness breaking back to single stack */
@media (max-width: 768px) {
    .fibonacci-grid {
        grid-template-columns: 1fr;
        gap: var(--f8);
        padding: var(--f5) var(--f3);
    }
    .panel-alpha {
        gap: var(--f3);
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
        border-bottom: 1px solid var(--border);
        padding-bottom: var(--f3);
    }
    .nav-links {
        flex-direction: row;
        gap: var(--f3);
    }
    .panel-beta {
        gap: var(--f8);
    }
    .constraints-header,
    .constraints-row {
        grid-template-columns: 110px 1fr 1fr;
    }
    .cta-section {
        flex-direction: column;
        align-items: flex-start;
    }
}