:root {
    color-scheme: dark;
    font-family: "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
    --bg: #0e1320;
    --fg: #f5f7ff;
    --muted: #8a94b5;
    --accent: #5b8def;
    --accent-strong: #88b6ff;
    --panel-bg: #161d31;
    --border: rgba(255, 255, 255, 0.08);
    --success: #4ade80;
    --danger: #f87171;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    background: radial-gradient(circle at top, rgba(76, 120, 255, 0.12), transparent 45%), var(--bg);
    color: var(--fg);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.shell {
    width: min(1100px, 100%);
    display: grid;
    grid-template-columns: minmax(0, 1fr);
    gap: 24px;
}

.masthead {
    display: flex;
    gap: 24px;
    align-items: center;
    justify-content: space-between;
    padding: 20px;
    border-radius: 16px;
    background: var(--panel-bg);
    border: 1px solid var(--border);
}

.masthead__langs {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: flex-end;
}

.lang-btn {
    border-radius: 999px;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--fg);
    padding: 8px 18px;
    cursor: pointer;
    transition: border-color 0.2s ease, transform 0.1s ease;
}

.lang-btn.is-active {
    border-color: var(--accent);
    transform: translateY(-1px);
}

.masthead__brand {
    display: flex;
    gap: 16px;
    align-items: center;
}

.brand__emblem {
    width: 56px;
    height: 56px;
    background: conic-gradient(from 120deg, var(--accent), transparent 65%);
    border-radius: 16px;
}

.masthead__stats {
    display: flex;
    gap: 20px;
}

.stat {
    display: grid;
    gap: 4px;
    text-align: center;
}

.stat__label {
    font-size: 12px;
    color: var(--muted);
    letter-spacing: 0.06em;
    text-transform: uppercase;
}

.stat__value {
    font-size: 24px;
    font-weight: 700;
}

.masthead__actions button {
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 999px;
    color: var(--fg);
    padding: 10px 22px;
    cursor: pointer;
    transition: border-color 0.2s ease, transform 0.1s ease;
}

.masthead__actions button:hover {
    border-color: var(--accent);
    transform: translateY(-1px);
}

.mode-switch {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 12px;
}

.mode-btn {
    padding: 14px 18px;
    border: 1px solid var(--border);
    background: var(--panel-bg);
    color: var(--fg);
    border-radius: 12px;
    cursor: pointer;
    transition: border-color 0.2s ease, background 0.3s ease;
    font-size: 16px;
}

.mode-btn.is-active {
    border-color: var(--accent);
    background: rgba(91, 141, 239, 0.18);
}

.playfield {
    display: grid;
    gap: 24px;
}

.panel {
    border: 1px solid var(--border);
    background: rgba(16, 20, 32, 0.68);
    border-radius: 18px;
    padding: 20px;
    display: grid;
    gap: 18px;
    min-height: 320px;
}

.panel header h2 {
    margin: 0;
}

.panel header p {
    margin: 6px 0 0;
    color: var(--muted);
}

.panel.is-hidden {
    display: none;
}

.panel__controls {
    display: flex;
    gap: 12px;
}

.primary {
    background: linear-gradient(135deg, var(--accent), var(--accent-strong));
    border: none;
    color: var(--fg);
    font-weight: 600;
    border-radius: 999px;
    cursor: pointer;
    padding: 10px 24px;
    transition: transform 0.1s ease, box-shadow 0.2s ease;
}

.primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 10px 24px rgba(91, 141, 239, 0.3);
}

.panel__board {
    display: grid;
    grid-template-columns: repeat(6, minmax(0, 1fr));
    gap: 8px;
    align-self: stretch;
}

.panel__board button {
    aspect-ratio: 1 / 1;
    border-radius: 10px;
    border: none;
    background: #1d253c;
    position: relative;
    cursor: pointer;
    transition: transform 0.1s ease, background 0.2s ease;
}

.panel__board button.is-on {
    background: #ffd166;
    box-shadow: 0 0 16px rgba(255, 209, 102, 0.5);
}

.panel__board button:active {
    transform: scale(0.95);
}

.sequence {
    display: grid;
    gap: 16px;
}

.sequence__display {
    min-height: 64px;
    background: rgba(12, 18, 30, 0.6);
    border: 1px solid var(--border);
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
}

.sequence__choices {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(72px, 1fr));
    gap: 12px;
}

.sequence__choices button {
    height: 72px;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: rgba(22, 30, 48, 0.7);
    color: var(--fg);
    font-size: 28px;
    cursor: pointer;
    transition: transform 0.1s ease, border-color 0.2s ease;
}

.sequence__choices button:active {
    transform: scale(0.96);
}

.sequence__choices button.highlight {
    border-color: var(--accent);
    box-shadow: 0 0 16px rgba(91, 141, 239, 0.4);
}

.shapes {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 20px;
}

.shape-grid {
    display: grid;
    grid-template-columns: repeat(5, minmax(0, 1fr));
    gap: 6px;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: rgba(14, 20, 32, 0.7);
}

.shape-grid--target {
    background: rgba(20, 28, 48, 0.7);
}

.shape-grid button,
.shape-grid span {
    width: 48px;
    height: 48px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: rgba(26, 32, 48, 0.8);
    cursor: pointer;
    transition: background 0.2s ease;
}

.shape-grid button.is-filled {
    background: linear-gradient(135deg, #f093fb, #f5576c);
    border-color: transparent;
    box-shadow: 0 0 12px rgba(245, 87, 108, 0.4);
}

.shape-grid--target span.is-filled {
    background: linear-gradient(135deg, #22d3ee, #3b82f6);
    border-color: transparent;
    box-shadow: 0 0 12px rgba(59, 130, 246, 0.4);
}

.hud {
    border: 1px solid var(--border);
    border-radius: 16px;
    background: rgba(14, 18, 32, 0.7);
    padding: 18px;
}

.hud__status {
    text-align: center;
    font-size: 18px;
    font-weight: 500;
}

.overlay {
    position: fixed;
    inset: 0;
    background: rgba(6, 8, 18, 0.8);
    display: grid;
    place-items: center;
    padding: 32px;
    backdrop-filter: blur(4px);
}

.overlay.hidden {
    display: none;
}

.overlay__content {
    background: rgba(18, 22, 34, 0.9);
    border-radius: 18px;
    padding: 32px;
    text-align: center;
    border: 1px solid var(--border);
    display: grid;
    gap: 16px;
}

@media (max-width: 768px) {
    body {
        padding: 16px;
    }

    .masthead,
    .panel,
    .hud,
    .overlay__content {
        border-radius: 14px;
    }

    .shape-grid button,
    .shape-grid span {
        width: 40px;
        height: 40px;
    }
}