/* Sudoku X — diagonal cell highlights */
.cell.diagonal {
    background: rgba(194,65,12,.06) !important;
}
.cell.diagonal.selected {
    background: var(--accent-glow) !important;
}
.cell.diagonal.highlighted {
    background: rgba(194,65,12,.09) !important;
}
.cell.diag-conflict {
    color: var(--error) !important;
    background: var(--error-bg) !important;
}
/* Subtle X watermark on the grid */
.grid-wrapper::before {
    content: '';
    position: absolute;
    inset: 0;
    background:
        linear-gradient(to bottom right, rgba(194,65,12,.035) 0%, transparent 50%),
        linear-gradient(to bottom left,  rgba(194,65,12,.035) 0%, transparent 50%);
    pointer-events: none;
    z-index: 1;
}