.grid-container {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  grid-gap: 15px;
}
.card {
  height: 100%;
}
#timer-display {
  text-align: center;
  width: 100px;
}

@media (max-width: 900px) {
  .grid-container {
    grid-template-columns: repeat(1, 1fr);
  }
}