:root {
    color-scheme: light;
    --bg: #ffffff;
    --surface: #ffffff;
    --surface-soft: #fafafa;
    --ink: #0f0f10;
    --ink-soft: #6b6b70;
    --line: #d4d4d4;
    --line-strong: #c0c0c0;
    --accent: #2f4ad0;
    --accent-soft: #eef1fc;
    --ok: #1f9d55;
    --ok-soft: #e7f6ec;
    --bad: #c53030;
    --bad-soft: #fdecec;
    --solid-color: #4a90d9;
    --liquid-color: #2f4ad0;
    --gas-color: #c53030;
    --shadow-card: 0 8px 24px -12px rgba(15, 15, 16, 0.18);
    --shadow-focus: 0 0 0 4px rgba(15, 15, 16, 0.06);
    --shadow-toplink: 0 4px 14px -6px rgba(15, 15, 16, 0.12);
}

[data-theme="dark"] {
    color-scheme: dark;
    --bg: #0c0c0e;
    --surface: #141418;
    --surface-soft: #1c1c21;
    --ink: #f5f5f7;
    --ink-soft: #9b9ba3;
    --line: #2e2e35;
    --line-strong: #44444c;
    --accent: #7c8fff;
    --accent-soft: #1c2244;
    --ok: #4ade80;
    --ok-soft: #102a1a;
    --bad: #f87171;
    --bad-soft: #2c1414;
    --solid-color: #5b9bd5;
    --liquid-color: #7c8fff;
    --gas-color: #f87171;
    --shadow-card: 0 8px 24px -8px rgba(0, 0, 0, 0.6);
    --shadow-focus: 0 0 0 4px rgba(124, 143, 255, 0.18);
    --shadow-toplink: 0 4px 14px -6px rgba(0, 0, 0, 0.6);
}

* {
    box-sizing: border-box;
}

html,
body {
    margin: 0;
    min-height: 100%;
}

body {
    background: var(--bg);
    color: var(--ink);
    font-family: -apple-system, BlinkMacSystemFont, "Inter", "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size: 16px;
    line-height: 1.55;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    letter-spacing: -0.005em;
}

a {
    color: inherit;
    text-decoration: none;
}

.skip-link {
    position: absolute;
    left: 16px;
    top: 16px;
    z-index: 30;
    background: var(--ink);
    color: var(--bg);
    padding: 10px 14px;
    border-radius: 8px;
    font-weight: 600;
    transform: translateY(-200%);
    transition: transform 120ms ease;
}

.skip-link:focus {
    transform: translateY(0);
}

.page {
    width: min(1120px, calc(100% - 40px));
    margin: 0 auto;
    padding: 20px 0 80px;
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 12px 0;
    border-bottom: 1px solid var(--line);
    margin-bottom: clamp(24px, 4vw, 36px);
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 0.95rem;
    letter-spacing: -0.01em;
}

.brand-mark {
    display: inline-grid;
    place-items: center;
    width: 28px;
    height: 28px;
    border-radius: 8px;
    background: var(--ink);
    color: var(--bg);
    font-size: 13px;
}

.brand-dot {
    color: var(--ink-soft);
    margin: 0 2px;
}

.nav-actions {
    display: inline-flex;
    align-items: center;
    gap: 14px;
}

.nav-tag {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--ink-soft);
    font-weight: 600;
}

.nav-tag i {
    font-size: 12px;
}

.theme-toggle {
    display: inline-grid;
    place-items: center;
    width: 38px;
    height: 38px;
    padding: 0;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--surface-soft);
    color: var(--ink);
    cursor: pointer;
    font-size: 14px;
    transition: background 120ms ease, border-color 120ms ease, color 120ms ease;
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
    background: var(--accent-soft);
    border-color: var(--accent);
    color: var(--accent);
    outline: 0;
}

.theme-toggle-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle-icon-light {
    display: inline-block;
}

:root:not([data-theme="dark"]) .theme-toggle-icon-dark {
    display: inline-block;
}

.breadcrumb {
    margin-bottom: 28px;
}

.breadcrumb a {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    min-height: 38px;
    padding: 8px 14px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: var(--surface-soft);
    color: var(--ink);
    font-size: 0.85rem;
    font-weight: 600;
    transition: background 120ms ease, border-color 120ms ease;
}

.breadcrumb a:hover,
.breadcrumb a:focus-visible {
    background: var(--accent-soft);
    border-color: var(--accent);
    color: var(--accent);
    outline: 0;
}

.breadcrumb i {
    font-size: 11px;
}

.hero {
    padding: clamp(20px, 4vw, 32px) 0 clamp(28px, 5vw, 48px);
    max-width: 880px;
}

.eyebrow {
    margin: 0 0 14px;
    font-size: 0.78rem;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--accent);
    font-weight: 600;
}

h1 {
    margin: 0;
    font-weight: 600;
    font-size: clamp(2.2rem, 6.5vw, 4.4rem);
    letter-spacing: -0.035em;
    line-height: 1.05;
    color: var(--ink);
}

.hero p {
    margin: 20px 0 0;
    max-width: 600px;
    font-size: clamp(1.05rem, 1.4vw, 1.2rem);
    color: var(--ink-soft);
}

/* Simulation section */
.sim-section {
    padding-top: clamp(28px, 4vw, 40px);
    border-top: 1px solid var(--line);
}

.sim-container {
    border: 1px solid var(--line);
    border-radius: 18px;
    background: var(--surface);
    padding: clamp(20px, 4vw, 32px);
    display: grid;
    gap: 20px;
}

.canvas-wrap {
    width: 100%;
}

#sim-canvas {
    display: block;
    border: 1px solid var(--line);
    border-radius: 14px;
    background: var(--surface-soft);
    max-width: 100%;
}

.sim-controls {
    display: grid;
    gap: 16px;
}

.temp-display {
    display: flex;
    align-items: baseline;
    gap: 16px;
    flex-wrap: wrap;
}

.temp-label {
    font-size: 0.78rem;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--ink-soft);
    font-weight: 600;
}

.temp-value {
    font-size: clamp(1.8rem, 4vw, 2.4rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--ink);
    line-height: 1;
}

.temp-state {
    font-size: 0.9rem;
    font-weight: 600;
    padding: 6px 14px;
    border-radius: 999px;
    background: var(--accent-soft);
    color: var(--accent);
    transition: background 200ms ease, color 200ms ease;
}

.temp-state.solid {
    background: #e3edfc;
    color: var(--solid-color);
}

.temp-state.liquid {
    background: var(--accent-soft);
    color: var(--liquid-color);
}

.temp-state.gas {
    background: var(--bad-soft);
    color: var(--gas-color);
}

[data-theme="dark"] .temp-state.solid {
    background: #152238;
}

.temp-slider-wrap {
    display: flex;
    align-items: center;
    gap: 14px;
}

.temp-min,
.temp-max {
    font-size: 0.82rem;
    color: var(--ink-soft);
    font-weight: 600;
    white-space: nowrap;
}

.temp-slider {
    flex: 1;
    -webkit-appearance: none;
    appearance: none;
    height: 8px;
    border-radius: 4px;
    background: linear-gradient(
        to right,
        var(--solid-color) 0%,
        var(--solid-color) 25%,
        var(--liquid-color) 25%,
        var(--liquid-color) 65%,
        var(--gas-color) 65%,
        var(--gas-color) 100%
    );
    outline: 0;
    cursor: pointer;
}

.temp-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--surface);
    border: 2px solid var(--ink);
    cursor: pointer;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.15);
}

.temp-slider::-moz-range-thumb {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--surface);
    border: 2px solid var(--ink);
    cursor: pointer;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.15);
}

.temp-slider:focus-visible {
    box-shadow: var(--shadow-focus);
}

.temp-legend {
    display: flex;
    justify-content: space-between;
    gap: 8px;
}

.legend-zone {
    flex: 1;
    text-align: center;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    padding: 6px 0;
    border-radius: 8px;
}

.legend-solid {
    background: #e3edfc;
    color: var(--solid-color);
}

.legend-liquid {
    background: var(--accent-soft);
    color: var(--liquid-color);
}

.legend-gas {
    background: var(--bad-soft);
    color: var(--gas-color);
}

[data-theme="dark"] .legend-solid {
    background: #152238;
}

/* Info display */
.sim-info {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    padding: 14px 18px;
    border: 1px solid var(--line);
    border-radius: 12px;
    background: var(--surface-soft);
    color: var(--ink);
    font-size: 0.92rem;
    min-height: 52px;
}

.sim-info i {
    color: var(--accent);
    font-size: 14px;
    margin-top: 2px;
    flex-shrink: 0;
}

.sim-info span {
    line-height: 1.5;
}

.foot {
    margin-top: 80px;
    padding-top: 24px;
    border-top: 1px solid var(--line);
    display: flex;
    justify-content: space-between;
    gap: 16px;
    font-size: 0.85rem;
    color: var(--ink-soft);
}

@media (max-width: 760px) {
    .nav {
        margin-bottom: 24px;
    }

    .temp-slider-wrap {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
    }

    .temp-min,
    .temp-max {
        text-align: center;
    }

    .temp-display {
        flex-direction: column;
        gap: 8px;
        align-items: flex-start;
    }
}