:root {
    --sudoku-bg-a: #07131f;
    --sudoku-bg-b: #0c2538;
    --sudoku-panel: rgba(8, 19, 34, 0.86);
    --sudoku-panel-soft: rgba(14, 33, 55, 0.92);
    --sudoku-line: rgba(149, 196, 255, 0.22);
    --sudoku-line-strong: rgba(149, 196, 255, 0.52);
    --sudoku-text: #e9f5ff;
    --sudoku-muted: #9bb8cf;
    --sudoku-accent: #7ff0d9;
    --sudoku-accent-strong: #31d5ff;
    --sudoku-gold: #ffd36f;
    --sudoku-danger: #ff7c8b;
}

.sudoku-page {
    background:
        radial-gradient(circle at top right, rgba(49, 213, 255, 0.18), transparent 34%),
        radial-gradient(circle at left center, rgba(127, 240, 217, 0.14), transparent 32%),
        linear-gradient(145deg, var(--sudoku-bg-a), var(--sudoku-bg-b));
    color: var(--sudoku-text);
    padding: 32px 18px 52px;
}

.sudoku-shell {
    margin: 0 auto;
    max-width: 1360px;
}

.sudoku-frame {
    background: var(--sudoku-panel);
    border: 1px solid var(--sudoku-line);
    border-radius: 30px;
    box-shadow: 0 28px 90px rgba(0, 0, 0, 0.32);
    overflow: hidden;
}

.sudoku-topbar,
.sudoku-main {
    display: grid;
    gap: 24px;
}

.sudoku-topbar {
    align-items: end;
    border-bottom: 1px solid rgba(149, 196, 255, 0.14);
    grid-template-columns: minmax(0, 1.6fr) minmax(280px, 1fr);
    padding: 30px;
}

.sudoku-kicker,
.sudoku-card-kicker {
    color: var(--sudoku-accent);
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.18em;
    margin: 0 0 10px;
    text-transform: uppercase;
}

.sudoku-brand h1 {
    font-size: clamp(2.2rem, 4vw, 4rem);
    line-height: 1;
    margin: 0 0 12px;
}

.sudoku-summary {
    color: var(--sudoku-muted);
    font-size: 1rem;
    margin: 0;
    max-width: 680px;
}

.sudoku-hud {
    display: grid;
    gap: 14px;
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.sudoku-hud-card,
.sudoku-mini-stat,
.sudoku-card {
    background: var(--sudoku-panel-soft);
    border: 1px solid rgba(149, 196, 255, 0.16);
    border-radius: 20px;
}

.sudoku-hud-card {
    display: flex;
    flex-direction: column;
    gap: 8px;
    min-height: 110px;
    padding: 18px;
}

.sudoku-hud-card span,
.sudoku-mini-stat span {
    color: var(--sudoku-muted);
    display: block;
    font-size: 0.84rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.sudoku-hud-card strong,
.sudoku-mini-stat strong {
    font-size: clamp(1.4rem, 2vw, 2rem);
    line-height: 1;
}

.sudoku-hud-card--millix strong,
.sudoku-mini-stat--accent strong {
    color: var(--sudoku-gold);
}

.sudoku-main {
    grid-template-columns: minmax(0, 1.45fr) minmax(300px, 0.85fr);
    padding: 30px;
}

.sudoku-board-panel,
.sudoku-side-panel {
    display: grid;
    gap: 22px;
}

.sudoku-toolbar,
.sudoku-controls,
.sudoku-claim-stats,
.sudoku-links {
    display: flex;
    gap: 14px;
}

.sudoku-toolbar,
.sudoku-controls {
    align-items: center;
    justify-content: space-between;
}

.sudoku-difficulty,
.sudoku-keypad,
.sudoku-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.sudoku-difficulty button,
.sudoku-keypad button,
.sudoku-button {
    appearance: none;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(149, 196, 255, 0.18);
    border-radius: 16px;
    color: var(--sudoku-text);
    cursor: pointer;
    font: inherit;
    transition: transform 0.18s ease, border-color 0.18s ease, background 0.18s ease;
}

.sudoku-difficulty button {
    padding: 10px 16px;
}

.sudoku-difficulty button.is-active,
.sudoku-difficulty button:hover,
.sudoku-keypad button:hover,
.sudoku-button:hover {
    border-color: rgba(127, 240, 217, 0.72);
    transform: translateY(-1px);
}

.sudoku-difficulty button.is-active {
    background: rgba(127, 240, 217, 0.12);
}

.sudoku-board-meta {
    display: flex;
    flex-direction: column;
    gap: 4px;
    text-align: right;
}

.sudoku-board-meta span {
    color: var(--sudoku-muted);
}

.sudoku-board-meta strong {
    color: var(--sudoku-gold);
    font-size: 1.6rem;
}

.sudoku-grid-wrap {
    background:
        linear-gradient(180deg, rgba(49, 213, 255, 0.06), transparent 16%),
        rgba(6, 15, 26, 0.78);
    border: 1px solid rgba(149, 196, 255, 0.16);
    border-radius: 28px;
    padding: 18px;
}

.sudoku-grid {
    display: grid;
    gap: 0;
    grid-template-columns: repeat(9, minmax(0, 1fr));
    margin: 0 auto;
    max-width: 720px;
}

.sudoku-cell {
    align-items: center;
    appearance: none;
    aspect-ratio: 1;
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--sudoku-line);
    color: var(--sudoku-text);
    cursor: pointer;
    display: flex;
    font-size: clamp(1rem, 2vw, 1.45rem);
    font-weight: 700;
    justify-content: center;
    min-height: 58px;
    transition: background 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}

.sudoku-cell:nth-child(3n) {
    border-right-color: var(--sudoku-line-strong);
}

.sudoku-cell:nth-child(9n + 1) {
    border-left-color: var(--sudoku-line-strong);
}

.sudoku-cell:nth-child(n + 19):nth-child(-n + 27),
.sudoku-cell:nth-child(n + 46):nth-child(-n + 54) {
    border-bottom-color: var(--sudoku-line-strong);
}

.sudoku-cell:nth-child(-n + 9),
.sudoku-cell:nth-child(n + 28):nth-child(-n + 36),
.sudoku-cell:nth-child(n + 55):nth-child(-n + 63) {
    border-top-color: var(--sudoku-line-strong);
}

.sudoku-cell.is-given {
    background: rgba(49, 213, 255, 0.08);
    color: var(--sudoku-accent-strong);
}

.sudoku-cell.is-selected {
    background: rgba(127, 240, 217, 0.14);
    border-color: rgba(127, 240, 217, 0.72);
}

.sudoku-cell.is-wrong {
    color: var(--sudoku-danger);
}

.sudoku-keypad button {
    flex: 1 1 56px;
    font-size: 1.15rem;
    min-height: 56px;
}

.sudoku-button {
    padding: 13px 18px;
}

.sudoku-button--secondary {
    background: rgba(255, 255, 255, 0.02);
}

.sudoku-card {
    padding: 22px;
}

.sudoku-claim-stats {
    display: grid;
    gap: 12px;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    margin-bottom: 18px;
}

.sudoku-mini-stat {
    padding: 14px;
}

.sudoku-status-note,
.sudoku-help,
.sudoku-guide span {
    color: var(--sudoku-muted);
    line-height: 1.6;
}

.sudoku-guide {
    display: grid;
    gap: 10px;
}

.sudoku-links {
    margin-top: 18px;
}

.sudoku-links a {
    color: var(--sudoku-accent);
    text-decoration: none;
}

.sudoku-recaptcha {
    margin-top: 18px;
}

@media (max-width: 1080px) {
    .sudoku-topbar,
    .sudoku-main {
        grid-template-columns: 1fr;
    }

    .sudoku-board-meta {
        text-align: left;
    }
}

@media (max-width: 720px) {
    .sudoku-page {
        padding: 18px 12px 40px;
    }

    .sudoku-topbar,
    .sudoku-main {
        padding: 18px;
    }

    .sudoku-hud,
    .sudoku-claim-stats {
        grid-template-columns: 1fr;
    }

    .sudoku-toolbar,
    .sudoku-controls {
        align-items: stretch;
        flex-direction: column;
    }

    .sudoku-actions {
        display: grid;
        grid-template-columns: 1fr 1fr;
    }
}