/* Sliding Puzzle */

.sp-stage {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.85rem;
    user-select: none;
}

.sp-hud {
    display: flex;
    gap: 1.5rem;
    font-weight: 600;
    color: var(--color-text-light);
    font-variant-numeric: tabular-nums;
}

.sp-board {
    --sp-size: 4;
    display: grid;
    grid-template-columns: repeat(var(--sp-size), 1fr);
    gap: 6px;
    width: min(400px, 90vw);
    aspect-ratio: 1;
    padding: 6px;
    background: var(--color-border-light);
    border-radius: var(--radius-md);
}

.sp-tile {
    border: none;
    border-radius: var(--radius-sm);
    background: var(--color-card-bg);
    color: var(--color-text);
    /* Scales with the grid so 5x5 stays readable on a phone. */
    font-size: calc(min(400px, 90vw) / var(--sp-size) * 0.42);
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    transition: background-color 100ms ease;
}

.sp-tile:hover { background: var(--color-primary); }

/* A tile already in its final square, so progress is visible at a glance. */
.sp-tile.home {
    background: var(--color-bg-secondary);
    color: var(--color-primary-dark);
}

.sp-tile.blank {
    background: transparent;
    box-shadow: none;
    cursor: default;
    pointer-events: none;
}

.sp-tile:focus-visible {
    outline: 3px solid var(--color-text);
    outline-offset: 2px;
}

.sp-sizes {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    justify-content: center;
}

.sp-size,
.sp-btn {
    padding: 0.55rem 1.15rem;
    font-size: 0.95rem;
    font-weight: 600;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-card-bg);
    color: var(--color-text);
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
}

.sp-btn {
    background: var(--color-primary);
    border-color: var(--color-primary-dark);
    padding: 0.75rem 2rem;
    font-size: 1.05rem;
}

.sp-size:hover { border-color: var(--color-primary-dark); }
.sp-size.active {
    background: var(--color-primary);
    border-color: var(--color-primary-dark);
}

.sp-size:focus-visible,
.sp-btn:focus-visible {
    outline: 3px solid var(--color-text);
    outline-offset: 2px;
}

.sp-feedback {
    min-height: 1.4em;
    margin: 0;
    font-weight: 600;
    color: var(--color-text-light);
    text-align: center;
}