.main div{
  display: block;
  height: 20px;
}

.elemSpan{
  height: 20px;
  width: 20px;
  display: inline-block;
}

.wallTrue{
  background: red;
}
.wallFalse{
  background: green;
}

.currentCell{
  background: yellow !important;
}

.finishCell{
  background: purple !important;
}