/* Light by default, dark via system preference */
:root {
    --bg: #f8fafc;
    --surface: #ffffff;
    --border: #e2e8f0;
    --text: #1e293b;
    --muted: #64748b;
    --accent: #b45309;
    --green: #16a34a;
    --red: #dc2626;
    --logo-text: #1e293b;
    --nav-bg: rgba(248, 250, 252, 0.92);
    --btn-primary-text: #ffffff;
    --inline-code-bg: #eef2f7;
    --inline-code-border: #dbe3ee;
    --inline-code-text: #334155;
    /* Code blocks stay dark in both themes */
    --code-bg: #1e293b;
    --code-surface: #0f172a;
    --code-border: #334155;
    --font-mono: "SFMono-Regular", Menlo, Monaco, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #0f172a;
        --surface: #1e293b;
        --border: #334155;
        --text: #e2e8f0;
        --muted: #94a3b8;
        --accent: #d97706;
        --green: #4ade80;
        --red: #f87171;
        --logo-text: #e2e8f0;
        --nav-bg: rgba(15, 23, 42, 0.92);
        --btn-primary-text: #0f172a;
        --inline-code-bg: #1e293b;
        --inline-code-border: #334155;
        --inline-code-text: #e2e8f0;
    }
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html {
    background: var(--bg);
    color: var(--text);
    font-family: system-ui, -apple-system, sans-serif;
    scroll-behavior: smooth;
}
body { overflow-x: hidden; }

/* ── Nav ────────────────────────────────────────────────────────────── */

.nav {
    position: sticky;
    top: 0;
    z-index: 50;
    background: var(--nav-bg);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
}

.nav-inner {
    max-width: 1320px;
    margin: 0 auto;
    padding: 0.65rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-width: 0;
}

.nav-brand { display: flex; align-items: center; text-decoration: none; }
.nav-logo { height: 28px; width: auto; }

.nav-links {
    display: flex;
    gap: 1.5rem;
    align-items: center;
    min-width: 0;
}

.nav-links a {
    color: var(--muted);
    text-decoration: none;
    font-size: 0.85rem;
    transition: color 0.15s;
}
.nav-links a:hover { color: var(--text); }

/* ── Hero ───────────────────────────────────────────────────────────── */

.hero {
    max-width: 1320px;
    margin: 0 auto;
    padding: 2.7rem 1.5rem 1.2rem;
    display: grid;
    grid-template-columns: minmax(0, 0.96fr) minmax(380px, 0.92fr);
    gap: 2.25rem;
    align-items: center;
}

.hero-text {
    padding-top: 0;
    min-width: 0;
}

.hero h1 {
    font-family: system-ui, -apple-system, sans-serif;
    font-size: clamp(2.28rem, 3.9vw, 3.55rem);
    font-weight: 790;
    line-height: 1;
    letter-spacing: -0.04em;
    margin-bottom: 0.85rem;
    max-width: 13.5ch;
}

.hero h1 span {
    color: var(--accent);
    opacity: 0.92;
}

.hero-thesis {
    display: block;
    font-size: 0.92rem;
    font-weight: 680;
    color: var(--accent);
    margin-bottom: 0.6rem;
    letter-spacing: -0.01em;
    line-height: 1.3;
}

.hero-sub {
    color: var(--muted);
    font-size: 1rem;
    line-height: 1.65;
    margin-bottom: 0.9rem;
    max-width: 44ch;
}

.hero-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem 0.75rem;
    margin-bottom: 0.95rem;
}

.hero-meta-item {
    display: inline-flex;
    align-items: center;
    font-size: 0.84rem;
    font-weight: 520;
    color: var(--muted);
}

.hero-meta-item::before {
    content: none;
}

.hero-meta-link {
    display: inline-flex;
    align-items: center;
    color: var(--accent);
    text-decoration: none;
    font-size: 0.84rem;
    font-weight: 650;
}

.hero-meta-link::before {
    content: "·";
    color: var(--muted);
    margin-right: 0.55rem;
}

.hero-meta-link:hover {
    text-decoration: underline;
    text-underline-offset: 0.16em;
}

.hero-cta {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 0.8rem;
}

.hero-proof {
    font-size: 0.78rem;
    color: var(--muted);
}
.hero-proof a {
    color: var(--muted);
    text-decoration: underline;
    text-underline-offset: 2px;
}
.hero-proof a:hover { color: var(--accent); }

.btn {
    display: inline-flex;
    align-items: center;
    padding: 0.72rem 1.25rem;
    border-radius: 12px;
    font-size: 0.9rem;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.15s;
}

.btn-primary {
    background: var(--accent);
    color: var(--btn-primary-text);
}
.btn-primary:hover { filter: brightness(1.15); }

.btn-secondary {
    background: transparent;
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-secondary:hover { border-color: var(--accent); color: var(--accent); }

/* Hero code */
.hero-code {
    position: relative;
    display: flex;
    justify-content: flex-end;
    padding-top: 0.6rem;
    min-width: 0;
}

.hero-window {
    position: relative;
    width: min(100%, 600px);
    max-width: 100%;
    border: 1px solid rgba(71, 85, 105, 0.72);
    border-radius: 14px;
    overflow: hidden;
    background: #202a3d;
    box-shadow: 0 6px 18px rgba(2, 8, 23, 0.1);
}

/* ── Shared code block ──────────────────────────────────────────────── */

.code-block {
    background: var(--code-bg);
    border: 1px solid var(--code-border);
    border-radius: 10px;
    color: #e2e8f0;
    padding: 1.25rem 1.5rem;
    font-family: var(--font-mono);
    font-size: 14px;
    line-height: 1.65;
    overflow-x: auto;
    white-space: pre;
    tab-size: 4;
}

.code-sm {
    font-size: 11.5px;
    padding: 0.7rem 0.85rem;
    border-radius: 8px;
    line-height: 1.55;
}

.hero-window .hero-code-block {
    margin: 0;
    border: none;
    border-radius: 0;
    background: transparent;
    padding: 1.2rem 1.35rem 1.25rem;
    font-size: 14px;
    line-height: 1.76;
}

/* Syntax colors (shared with playground) */
.hl-keyword { color: #c084fc; }
.hl-fn { color: #67e8f9; }
.hl-type { color: #fde68a; }
.hl-builtin { color: #fde68a; }
.hl-string { color: #86efac; }
.hl-desc { color: #86efac; font-style: italic; }
.hl-number { color: #fda4af; }
.hl-constant { color: #fda4af; }
.hl-comment { color: #64748b; font-style: italic; }
.hl-effect { color: #f97316; font-weight: 600; }
.hl-operator { color: #94a3b8; }
.hl-muted { color: #64748b; }
.hl-green { color: #4ade80; }
.hl-red { color: #f87171; }

/* ── Features ───────────────────────────────────────────────────────── */

.features, .games, .start {
    max-width: 1320px;
    margin: 0 auto;
    padding: 2.5rem 1.5rem;
}

.features {
    padding-top: 0.5rem;
}

.features h2, .games h2, .start h2 {
    font-size: 1.75rem;
    margin-bottom: 0.5rem;
    letter-spacing: -0.01em;
}

.section-sub {
    color: var(--muted);
    margin-bottom: 2rem;
    font-size: 1rem;
}

.features h2 { margin-bottom: 1.25rem; }

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.1rem;
}

.feature-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 1.35rem;
    transition: border-color 0.2s, box-shadow 0.2s;
    box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    min-width: 0;
}
.feature-card:hover {
    border-color: var(--accent);
    box-shadow: 0 6px 18px rgba(15, 23, 42, 0.06);
}

.feature-card h3 {
    font-size: 1.02rem;
    margin-bottom: 0.5rem;
    color: var(--accent);
}

.feature-card p {
    color: var(--muted);
    font-size: 0.87rem;
    line-height: 1.58;
    margin-bottom: 1rem;
}

.feature-card em {
    font-style: normal;
    color: var(--text);
}

.feature-card .code-block {
    background: var(--code-surface);
    box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.06);
}

/* ── Constraints ───────────────────────────────────────────────────── */

.constraints {
    max-width: 1320px;
    margin: 0 auto;
    padding: 2.5rem 1.5rem;
}

.constraints h2 {
    font-size: 1.75rem;
    margin-bottom: 0.5rem;
    letter-spacing: -0.01em;
}

.constraints-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.75rem;
    margin-top: 2rem;
}

.constraint {
    display: flex;
    gap: 0.75rem;
    align-items: baseline;
    padding: 0.85rem 1rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}

.constraint-absent {
    flex-shrink: 0;
    font-weight: 700;
    font-size: 0.85rem;
    color: var(--accent);
    min-width: 120px;
}

.constraint-absent code {
    background: var(--inline-code-bg);
    color: var(--inline-code-text);
    border: 1px solid var(--inline-code-border);
    padding: 0.08rem 0.4rem;
    border-radius: 5px;
    font-size: 0.8rem;
    font-weight: 650;
    letter-spacing: -0.01em;
    white-space: nowrap;
}

.constraint-instead {
    font-size: 0.82rem;
    color: var(--muted);
    line-height: 1.45;
}

.constraint-instead code {
    background: var(--inline-code-bg);
    color: var(--inline-code-text);
    border: 1px solid var(--inline-code-border);
    padding: 0.08rem 0.4rem;
    border-radius: 5px;
    font-size: 0.78rem;
    font-weight: 650;
    letter-spacing: -0.01em;
    white-space: nowrap;
}

/* ── Games ──────────────────────────────────────────────────────────── */

.games { text-align: center; }
.games h2 { margin-bottom: 0.5rem; }

.games-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    justify-content: center;
    margin-top: 2rem;
}

.game-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    padding: 1.25rem 1.5rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    text-decoration: none;
    color: var(--text);
    font-size: 0.85rem;
    font-weight: 500;
    min-width: 120px;
    transition: all 0.2s;
    box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}
.game-card:hover {
    border-color: var(--accent);
    transform: translateY(-2px);
}

.game-icon {
    font-size: 2rem;
    line-height: 1;
}

.game-card small {
    font-size: 0.7rem;
    font-weight: 400;
    color: var(--muted);
    opacity: 0.7;
}

/* ── Getting started ────────────────────────────────────────────────── */

.start-steps {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.25rem;
    margin-top: 2rem;
}

.step {
    display: flex;
    gap: 1rem;
    align-items: flex-start;
}

.step-num {
    flex-shrink: 0;
    width: 2rem;
    height: 2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--accent);
    color: var(--btn-primary-text);
    font-weight: 700;
    font-size: 0.85rem;
}

.step-body { flex: 1; min-width: 0; }

.step-body h3 {
    font-size: 0.95rem;
    margin-bottom: 0.5rem;
}

/* ── Footer ─────────────────────────────────────────────────────────── */

.footer {
    margin-top: 1.5rem;
    border-top: 1px solid var(--border);
    padding: 2rem 1.5rem;
}

.footer-inner {
    max-width: 1320px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.footer-brand {
    font-weight: 700;
    color: var(--accent);
    font-size: 1.1rem;
}

.footer-links {
    display: flex;
    gap: 1.5rem;
}

.footer-links a {
    color: var(--muted);
    text-decoration: none;
    font-size: 0.85rem;
}
.footer-links a:hover { color: var(--accent); }

/* ── Responsive ─────────────────────────────────────────────────────── */

@media (max-width: 1100px) {
    .features-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
    .nav-inner {
        flex-wrap: wrap;
        row-gap: 0.7rem;
        align-items: flex-start;
    }
    .nav-links {
        width: 100%;
        justify-content: space-between;
        gap: 0.85rem;
        flex-wrap: wrap;
    }
    .hero {
        grid-template-columns: 1fr;
        padding: 2.4rem 1.25rem 1rem;
        gap: 1.4rem;
    }
    .hero h1 {
        font-size: 2.02rem;
        max-width: none;
    }
    .hero-thesis {
        font-size: 0.88rem;
        letter-spacing: -0.015em;
    }
    .hero-sub { font-size: 1rem; }
    .hero-meta {
        flex-direction: column;
        align-items: flex-start;
    }
    .hero-code {
        padding-top: 0;
        justify-content: stretch;
    }
    .hero-window {
        width: 100%;
    }
    .hero-window .hero-code-block {
        padding: 1rem 1rem 1.05rem;
        font-size: 13px;
        line-height: 1.68;
    }

    .features-grid { grid-template-columns: 1fr; }
    .constraints-grid { grid-template-columns: 1fr; }
    .start-steps { grid-template-columns: 1fr; }

    .nav-links a { font-size: 0.8rem; }

    .footer-inner {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }
    .footer-links { flex-wrap: wrap; justify-content: center; }
}

@media (max-width: 480px) {
    .hero h1 { font-size: 1.72rem; }
    .hero-thesis { font-size: 0.84rem; }
    .hero-meta-link, .hero-meta-item { font-size: 0.8rem; }
    .hero-cta { flex-direction: column; }
    .hero-cta .btn { justify-content: center; }
    .nav-links {
        gap: 0.5rem 0.9rem;
        justify-content: flex-start;
    }
    .nav-links a:not(:last-child):not(:nth-last-child(2)) { display: none; }
    .hero-window .hero-code-block {
        padding: 0.92rem 0.9rem 1rem;
        font-size: 12px;
        line-height: 1.6;
    }
    .games-grid { gap: 0.6rem; }
    .game-card { min-width: 90px; padding: 1rem; }
}