:root {
    --bg: #0f172a;
    --panel-bg: #1e293b;
    --text: #f1f5f9;
    --text-dim: #94a3b8;
    --border: #334155;
    --btn-bg: #334155;
    --btn-hover: #475569;
    --color-a: #f97316;
    --color-b: #38bdf8;
    --color-lcd: #a78bfa;
}

*, *::before, *::after { box-sizing: border-box; }

body {
    font-family: 'Outfit', sans-serif;
    background: var(--bg);
    color: var(--text);
    margin: 0;
    display: flex;
    min-height: 100vh;
}

/* Side panel */
#ui-panel {
    width: 240px;
    min-width: 240px;
    background: var(--panel-bg);
    padding: 1.5rem 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    border-right: 1px solid var(--border);
    overflow-y: auto;
}

.back-link {
    color: var(--text-dim);
    text-decoration: none;
    font-size: 0.875rem;
    transition: color 0.2s;
}
.back-link:hover { color: var(--text); }

.app-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin: 0;
    color: var(--color-a);
}

.section { display: flex; flex-direction: column; gap: 0.5rem; }

.section-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-dim);
}

/* Fraction control widget */
.fraction-control {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 0.75rem;
    padding: 0.75rem 1rem;
}

.fraction-row {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.fraction-number {
    font-size: 1.75rem;
    font-weight: 600;
    min-width: 2ch;
    text-align: center;
    line-height: 1;
}

.fraction-bar {
    width: 4rem;
    height: 2px;
    background: var(--text-dim);
    border-radius: 1px;
    margin: 0.15rem 0;
}

.adjust-btn {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    border: none;
    background: var(--btn-bg);
    color: var(--text);
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background 0.15s;
    user-select: none;
    -webkit-user-select: none;
    touch-action: none;
}
.adjust-btn:hover { background: var(--btn-hover); }
.adjust-btn:active { background: #64748b; }

/* Sum */
.sum-section { gap: 0.3rem; }

.sum-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-dim);
}

.sum-formula {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text);
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    padding: 0.4rem 0.75rem;
    text-align: center;
}

/* LCD button */
.lcd-btn {
    background: transparent;
    border: 2px solid var(--color-lcd);
    color: var(--color-lcd);
    border-radius: 0.6rem;
    padding: 0.5rem 0.75rem;
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s, color 0.2s;
}
.lcd-btn:hover, .lcd-btn.active {
    background: var(--color-lcd);
    color: #0f172a;
}

/* Legend */
.legend {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    margin-top: auto;
}
.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    color: var(--text-dim);
}
.legend-swatch {
    width: 1rem;
    height: 1rem;
    border-radius: 0.2rem;
    flex-shrink: 0;
}

/* Main viz area */
#viz-area {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem;
}

#pizzas-row {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    flex-wrap: wrap;
    justify-content: center;
}

.pizza-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.pizza-wrapper svg {
    width: min(180px, 28vw);
    height: min(180px, 28vw);
    filter: drop-shadow(0 4px 16px rgba(0,0,0,0.5));
}

.pizza-label {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text);
    letter-spacing: 0.03em;
}

.plus-sign {
    font-size: 2.5rem;
    font-weight: 300;
    color: var(--text-dim);
    user-select: none;
}

@media (max-width: 700px) {
    body { flex-direction: column; }
    #ui-panel {
        width: 100%;
        min-width: unset;
        border-right: none;
        border-bottom: 1px solid var(--border);
        flex-direction: row;
        flex-wrap: wrap;
        gap: 1rem;
        padding: 1rem;
    }
    .app-title { width: 100%; }
    .legend { flex-direction: row; margin-top: 0; }
    #pizzas-row { gap: 0.75rem; }
    .plus-sign { font-size: 1.75rem; }
}