.sudoku-cell {
    width: 35px;
    height: 35px;
}
.sudoku-cell:nth-child(3n) {
    border-right: 2px solid #4a5568;
}
.sudoku-row:nth-child(3n) .sudoku-cell {
    border-bottom: 2px solid #4a5568;
}

#fireworks-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 9999;
}

.sudoku-cell[readonly] {
    color: #666;
    background-color: #eee;
}

.error {
/*     color: red;
    font-weight: bold; */
  }