.rules { 
    font-family: sans-serif;
    text-align: center;
    margin: 0;
    line-height: 1.9;
    padding: 10px;
    background: #fff;
    font-size: 14px;
}
#grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(24px, 1fr));
  grid-gap: 3px;
  max-width: 1000px;
  margin: 10px auto;
}
.tile {
  width: 100%;
  aspect-ratio: 1;
  background: green;
  color: white;
  font-size: 12px;
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  border-radius: 4px;
}
.tile.opened {
  background: gray;
  pointer-events: none;
}