:root {
    --surface-1: #fcfcfb;
    --page: #f9f9f7;
    --text-primary: #0b0b0b;
    --text-secondary: #52514e;
    --text-muted: #898781;
    --grid-line: #e1e0d9;
    --baseline: #c3c2b7;
    --border: rgba(11, 11, 11, 0.10);
    --series-1: #2a78d6;
    --series-2: #1baf7a;
    --series-3: #eda100;
    --series-8: #eb6834;
    --accent: #2a78d6;
    --accent-ink: #ffffff;
}

@media (prefers-color-scheme: dark) {
    :root {
        --surface-1: #1a1a19;
        --page: #0d0d0d;
        --text-primary: #ffffff;
        --text-secondary: #c3c2b7;
        --text-muted: #898781;
        --grid-line: #2c2c2a;
        --baseline: #383835;
        --border: rgba(255, 255, 255, 0.10);
        --series-1: #3987e5;
        --series-2: #199e70;
        --series-3: #c98500;
        --series-8: #d95926;
        --accent: #3987e5;
    }
}

* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
    background: var(--page);
    color: var(--text-primary);
    font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
    line-height: 1.5;
}

/* ---------- shell ---------- */

.app-shell {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.25rem 2rem;
}

.app-header {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 0.75rem;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border);
    margin-bottom: 1.25rem;
}

.app-title {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    font-weight: 650;
    font-size: 1.05rem;
}

.app-byline {
    color: var(--text-muted);
    font-weight: 400;
    font-size: 0.82rem;
    margin-left: 0.4rem;
    text-decoration: none;
}

.app-byline:hover {
    text-decoration: underline;
    color: var(--text-secondary);
}

.app-mark {
    width: 18px;
    height: 18px;
    border-radius: 4px;
    background:
        linear-gradient(45deg,
            var(--text-primary) 0 25%, var(--surface-1) 25% 50%,
            var(--text-primary) 50% 75%, var(--surface-1) 75%);
    border: 1px solid var(--border);
}

.app-nav {
    display: flex;
    gap: 0.25rem;
    flex-wrap: wrap;
}

.app-nav a {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 0.35rem 0.7rem;
    border-radius: 8px;
    font-size: 0.92rem;
}

.app-nav a:hover {
    background: var(--grid-line);
}

.app-nav a.active {
    color: var(--text-primary);
    background: var(--grid-line);
    font-weight: 600;
}

.app-footer {
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border);
    color: var(--text-muted);
    font-size: 0.85rem;
}

.app-footer a {
    color: var(--text-secondary);
}

.page-title {
    font-size: 1.35rem;
    margin: 0 0 0.4rem;
}

.page-title:focus {
    outline: none;
}

.page-intro {
    color: var(--text-secondary);
    max-width: 62rem;
    margin-top: 0;
}

/* ---------- scene layout ---------- */

.sim-layout {
    display: grid;
    grid-template-columns: minmax(280px, 1fr) minmax(260px, 340px);
    gap: 1.25rem;
    align-items: start;
}

@media (max-width: 900px) {
    .sim-layout {
        grid-template-columns: 1fr;
    }
}

.scene-panel {
    background: var(--surface-1);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 0.9rem;
    min-width: 0;
}

.scene-viewport {
    position: relative;
    width: 100%;
    aspect-ratio: 4 / 3;
    border: 1px solid var(--grid-line);
    border-radius: 6px;
    overflow: hidden;
    background: transparent;
    touch-action: none;
}

.scene-viewport canvas {
    display: block;
    width: 100%;
    height: 100%;
}

.scene-hint {
    font-size: 0.78rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
}

.scene-legend {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    margin-top: 0.75rem;
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.scene-legend-bar {
    flex: 1;
    height: 10px;
    border-radius: 5px;
    background: linear-gradient(to right, #2a78d6, #dbd9d1, #eb6834);
    border: 1px solid var(--border);
}

.readout-row {
    display: flex;
    flex-wrap: wrap;
    gap: 1.25rem;
    margin-top: 0.75rem;
}

.readout {
    display: flex;
    flex-direction: column;
}

.readout-label {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.readout-value {
    font-size: 1.05rem;
    font-weight: 600;
    font-variant-numeric: tabular-nums;
}

/* ---------- controls ---------- */

.controls {
    background: var(--surface-1);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1rem;
    display: flex;
    flex-direction: column;
    gap: 1.1rem;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.control-buttons {
    flex-direction: row;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.control-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.control-hint {
    font-size: 0.78rem;
    color: var(--text-muted);
}

.inline-controls {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.btn {
    font: inherit;
    font-size: 0.9rem;
    padding: 0.45rem 0.9rem;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--surface-1);
    color: var(--text-primary);
    cursor: pointer;
}

.btn:hover:not(:disabled) {
    background: var(--grid-line);
}

.btn:disabled {
    opacity: 0.45;
    cursor: default;
}

.btn-primary {
    background: var(--accent);
    border-color: var(--accent);
    color: var(--accent-ink);
    min-width: 5.5rem;
}

.btn-primary:hover:not(:disabled) {
    filter: brightness(1.08);
    background: var(--accent);
}

.btn-active {
    background: var(--accent);
    color: var(--accent-ink);
    border-color: var(--accent);
}

.segmented {
    display: flex;
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
    width: fit-content;
}

.seg-btn {
    font: inherit;
    font-size: 0.85rem;
    padding: 0.4rem 0.75rem;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
}

.seg-btn + .seg-btn {
    border-left: 1px solid var(--border);
}

.seg-btn-active {
    background: var(--accent);
    color: var(--accent-ink);
    font-weight: 600;
}

.check-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

input[type="range"] {
    width: 100%;
    accent-color: var(--accent);
}

select,
input[type="number"] {
    font: inherit;
    font-size: 0.88rem;
    padding: 0.3rem 0.45rem;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--surface-1);
    color: var(--text-primary);
}

.slider-scale {
    position: relative;
    display: flex;
    justify-content: space-between;
    font-size: 0.72rem;
    color: var(--text-muted);
    height: 1.1rem;
}

/* ---------- explainer ---------- */

.explainer {
    background: var(--surface-1);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.1rem 1.4rem;
    margin-top: 1.25rem;
    max-width: 62rem;
}

.explainer h2 {
    font-size: 1.05rem;
    margin: 0 0 0.6rem;
}

.explainer h2:not(:first-child) {
    margin-top: 1.5rem;
}

.explainer-list {
    color: var(--text-secondary);
    margin: 0.6rem 0;
    padding-left: 1.2rem;
}

.explainer-list li {
    margin: 0.5rem 0;
}

.explainer-list strong {
    color: var(--text-primary);
}

.explainer p {
    color: var(--text-secondary);
    margin: 0.6rem 0;
}

.explainer strong {
    color: var(--text-primary);
}

.explainer [data-katex-display] {
    margin: 0.9rem 0;
    overflow-x: auto;
    overflow-y: hidden;
    padding: 0.3rem 0;
}

.explainer .katex-display {
    margin: 0;
}

.page-intro .katex,
.explainer p .katex,
.explainer li .katex {
    font-size: 1em;
}

/* ---------- loading & error UI ---------- */

.app-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 70vh;
    color: var(--text-secondary);
}

.app-loading-grid {
    width: 48px;
    height: 48px;
    border-radius: 8px;
    background:
        linear-gradient(45deg,
            var(--text-primary) 0 25%, var(--grid-line) 25% 50%,
            var(--text-primary) 50% 75%, var(--grid-line) 75%);
    animation: pulse 1.2s ease-in-out infinite alternate;
    margin-bottom: 1rem;
}

@keyframes pulse {
    from { opacity: 0.4; }
    to { opacity: 1; }
}

.loading-progress-text {
    font-variant-numeric: tabular-nums;
    font-weight: 600;
}

.loading-progress-text::after {
    content: var(--blazor-load-percentage-text, "");
}

#blazor-error-ui {
    color-scheme: light only;
    background: lightyellow;
    color: #0b0b0b;
    bottom: 0;
    box-shadow: 0 -1px 4px rgba(0, 0, 0, 0.2);
    display: none;
    left: 0;
    padding: 0.6rem 1.25rem 0.7rem 1.25rem;
    position: fixed;
    width: 100%;
    z-index: 1000;
}

#blazor-error-ui .dismiss {
    cursor: pointer;
    position: absolute;
    right: 0.75rem;
    top: 0.5rem;
}