:root {
    --sudoku-line: var(--border);
    --sudoku-box-line: var(--text-2);
    --sudoku-given: var(--text);
    --sudoku-entered: var(--brand);
    --sudoku-related: color-mix(in srgb, var(--brand) 9%, var(--surface));
    --sudoku-same-box: color-mix(in srgb, var(--text) 3%, var(--surface));
}

.sudoku-stars {
    color: var(--tile-present);
    letter-spacing: 0.05em;
}

/* --- Index --- */

.sudoku-card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
    gap: var(--space-4);
}

.sudoku-card {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
    padding: var(--space-4);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    background: var(--surface);
    color: inherit;
    text-decoration: none;
    box-shadow: var(--shadow-sm);
    transition: transform 0.15s, box-shadow 0.15s, border-color 0.15s;
}

.sudoku-card:hover {
    transform: translateY(-2px);
    border-color: var(--brand);
    box-shadow: var(--shadow);
    color: inherit;
    text-decoration: none;
}

.sudoku-preview {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    aspect-ratio: 1;
    border: 2px solid var(--sudoku-box-line);
    border-radius: 6px;
    overflow: hidden;
    background: var(--surface);
}

.sudoku-preview-cell {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: clamp(0.4rem, 1.8vw, 0.62rem);
    font-weight: 700;
    color: var(--sudoku-given);
    border-right: 1px solid var(--sudoku-line);
    border-bottom: 1px solid var(--sudoku-line);
}

.sudoku-preview-cell.box-right {
    border-right: 2px solid var(--sudoku-box-line);
}

.sudoku-preview-cell.box-bottom {
    border-bottom: 2px solid var(--sudoku-box-line);
}

.sudoku-preview-cell.has-value {
    background: var(--surface-2);
}

.sudoku-card-meta {
    display: flex;
    flex-direction: column;
    gap: 2px;
    font-size: 0.9rem;
}

.sudoku-difficulty {
    font-weight: 800;
}

.sudoku-clues {
    color: var(--muted);
    font-size: 0.85rem;
}

.sudoku-random-actions {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: var(--space-2);
}

.sudoku-random-actions form {
    margin: 0;
}

.sudoku-random-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
    width: 100%;
    padding: var(--space-3) var(--space-2);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--surface-2);
    font-weight: 700;
    transition: border-color 0.15s, background 0.15s;
}

.sudoku-random-btn:hover {
    border-color: var(--brand);
    background: var(--brand-soft);
}

.sudoku-archive-day {
    padding: var(--space-3) 0;
    border-bottom: 1px solid var(--border);
}

.sudoku-archive-date {
    margin: 0 0 var(--space-2);
    font-size: 0.92rem;
    color: var(--muted);
}

/* --- Play --- */

.sudoku-page {
    width: 100%;
    overflow-x: clip;
}

.sudoku-head {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: var(--space-4);
    max-width: 760px;
    margin: 0 auto var(--space-4);
}

.sudoku-back {
    display: inline-block;
    margin-bottom: var(--space-1);
    font-size: 0.9rem;
}

.sudoku-title {
    margin: 0;
    font-size: clamp(1.2rem, 4vw, 1.6rem);
}

.sudoku-meta {
    margin: var(--space-1) 0 0;
    color: var(--muted);
    font-size: 0.92rem;
}

.sudoku-timer {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    padding: var(--space-2) var(--space-3);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--surface);
}

.sudoku-timer-label {
    font-size: 0.72rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--muted);
}

.sudoku-timer strong {
    font-size: 1.2rem;
    font-variant-numeric: tabular-nums;
}

.sudoku-play-layout {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    max-width: 760px;
    margin: 0 auto var(--space-5);
    min-width: 0;
}

.sudoku-board-wrap {
    width: 100%;
    max-width: min(460px, 100%);
    margin-inline: auto;
}

.sudoku-board {
    display: grid;
    grid-template-columns: repeat(9, minmax(0, 1fr));
    grid-template-rows: repeat(9, minmax(0, 1fr));
    width: 100%;
    aspect-ratio: 1;
    border: 3px solid var(--sudoku-box-line);
    border-radius: var(--radius-sm);
    overflow: hidden;
    background: var(--surface);
    box-shadow: var(--shadow);
}

.sudoku-cell {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    min-width: 0;
    min-height: 0;
    margin: 0;
    padding: 0;
    border: 0;
    border-right: 1px solid var(--sudoku-line);
    border-bottom: 1px solid var(--sudoku-line);
    background: var(--surface);
    color: var(--sudoku-entered);
    font-size: clamp(0.95rem, 4.2vw, 1.6rem);
    font-weight: 700;
    touch-action: manipulation;
}

.sudoku-cell.border-right {
    border-right: 2px solid var(--sudoku-box-line);
}

.sudoku-cell.border-bottom {
    border-bottom: 2px solid var(--sudoku-box-line);
}

.sudoku-cell.shade {
    background: var(--sudoku-same-box);
}

.sudoku-cell.given {
    color: var(--sudoku-given);
    font-weight: 800;
    cursor: default;
}

.sudoku-cell.related {
    background: var(--sudoku-related);
}

.sudoku-cell.selected {
    position: relative;
    z-index: 2;
    background: color-mix(in srgb, var(--brand) 22%, var(--surface));
    outline: 2px solid var(--brand);
    outline-offset: -2px;
}

.sudoku-cell.error {
    color: var(--danger);
    background: var(--danger-soft);
}

.sudoku-status {
    min-height: 1.4rem;
    margin: 0;
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 600;
    text-align: center;
}

.sudoku-status.win {
    color: var(--ok);
}

.sudoku-controls {
    width: 100%;
    max-width: min(460px, 100%);
    margin-inline: auto;
}

.sudoku-panel {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    grid-template-rows: repeat(4, minmax(3rem, auto));
    gap: var(--space-2);
}

.sudoku-digits {
    display: contents;
}

.sudoku-digit:nth-child(1) { grid-column: 1; grid-row: 2; }
.sudoku-digit:nth-child(2) { grid-column: 2; grid-row: 2; }
.sudoku-digit:nth-child(3) { grid-column: 3; grid-row: 2; }
.sudoku-digit:nth-child(4) { grid-column: 1; grid-row: 3; }
.sudoku-digit:nth-child(5) { grid-column: 2; grid-row: 3; }
.sudoku-digit:nth-child(6) { grid-column: 3; grid-row: 3; }
.sudoku-digit:nth-child(7) { grid-column: 1; grid-row: 4; }
.sudoku-digit:nth-child(8) { grid-column: 2; grid-row: 4; }
.sudoku-digit:nth-child(9) { grid-column: 3; grid-row: 4; }

#sudoku-clear { grid-column: 1; grid-row: 1; }
.sudoku-mode { grid-column: 2 / span 2; grid-row: 1; }
#sudoku-undo { grid-column: 4; grid-row: 1; }
#sudoku-redo { grid-column: 4; grid-row: 2; }
#sudoku-erase { grid-column: 4; grid-row: 3; }
#sudoku-hint { grid-column: 4; grid-row: 4; }

.sudoku-digit {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-size: 1.25rem;
    font-weight: 800;
    box-shadow: var(--shadow-sm);
    touch-action: manipulation;
    transition: background 0.1s, border-color 0.1s;
}

.sudoku-digit:hover {
    background: var(--surface-2);
}

.sudoku-digit.active {
    border-color: var(--brand);
    background: var(--brand);
    color: var(--brand-contrast);
}

.sudoku-tool {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface-2);
    color: var(--text-2);
    touch-action: manipulation;
}

.sudoku-tool svg {
    width: 1.3rem;
    height: 1.3rem;
}

.sudoku-tool:hover {
    background: var(--surface-3);
    color: var(--text);
}

.sudoku-tool:active {
    transform: translateY(1px);
}

.sudoku-tool--hint {
    border-color: color-mix(in srgb, var(--tile-present) 50%, var(--border));
    background: color-mix(in srgb, var(--tile-present) 16%, var(--surface));
    color: var(--warn);
}

.sudoku-mode {
    display: flex;
    margin: 0;
    padding: 0;
    min-width: 0;
}

.sudoku-mode-toggle {
    display: flex;
    width: 100%;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    background: var(--surface-2);
}

.sudoku-mode-option {
    position: relative;
    flex: 1;
    margin: 0;
    cursor: pointer;
}

.sudoku-mode-option input {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
    margin: 0;
}

.sudoku-mode-option span {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    padding: 0 var(--space-2);
    font-size: 0.88rem;
    font-weight: 700;
    color: var(--muted);
    user-select: none;
    transition: background 0.12s, color 0.12s;
}

.sudoku-mode-option input:checked + span {
    background: var(--brand);
    color: var(--brand-contrast);
}

.sudoku-mode-option input:focus-visible + span {
    outline: 2px solid var(--brand);
    outline-offset: -2px;
}

@media (min-width: 900px) {
    .sudoku-play-layout {
        display: grid;
        grid-template-columns: minmax(0, 1fr) 260px;
        gap: var(--space-5);
        align-items: start;
    }

    .sudoku-board-wrap,
    .sudoku-status {
        grid-column: 1;
    }

    .sudoku-controls {
        grid-column: 2;
        grid-row: 1 / span 2;
        margin: 0;
    }

    .sudoku-panel {
        grid-template-rows: repeat(4, 3.5rem);
    }
}