.th-board {
  display: grid;
  gap: 2px;
  margin: 6px auto;
  background: #e7ecf3;
  padding: 5px;
  border-radius: 10px;
  width: max-content;
}
.th-cell {
  width: 34px;
  height: 34px;
  background: #fff;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  position: relative;
  user-select: none;
  font-size: 18px;
  transition: background .12s;
}
.th-cell.bulb {
  background: #f4f7fb;
}
.th-cell.bulb::after {
  content: "";
  position: absolute;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #c4cedb;
}
.th-cell.filled {
  background: #4d96ff;
}
.th-cell.filled::after { display: none; }
.th-cell.filled.bulb::after {
  background: #2f6fd6;
}
.th-clue {
  display: grid;
  gap: 2px;
  margin: 2px auto;
}
.th-clue span {
  width: 34px;
  height: 20px;
  line-height: 20px;
  text-align: center;
  font-size: 13px;
  font-weight: 700;
  color: #3a4a5e;
  background: #eef3f9;
  border-radius: 4px;
}
.th-clue.row { grid-auto-flow: column; }