.block {
    width: 64px;
    height: 64px;
    float: left;
}

.blocked {
    background-color: red;
}

.hint {
    background-color: green;
}

@media screen and (max-width: 780px) {
  .block {
      width: 48px;
      height: 48px;
  }
}

@media screen and (max-width: 550px) {
  .block {
      width: 32px;
      height: 32px;
  }
}