#keyboard {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin-top: 20px;
}

.keyboard-row {
  width:100%;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
}

.key {
  width: 40px;
  height: 40px;
  margin: 5px;
  font-size: 18px;
  text-align: center;
  line-height: 40px;
  background-color: #ddd;
  border: 1px solid #aaa;
  border-radius: 5px;
  cursor: pointer;
}

.key.green {
  background-color: #6aaa64;
  color: white;
}

.key.yellow {
  background-color: #c9b458;
  color: white;
}

.key.grey {
  background-color: #787c7e;
  color: white;
}

@media (max-width: 600px) {
  #keyboard {
    width: 100%;
    padding: 0;
  }

  .keyboard-row {
    width: 10%;
    display: flex;
    justify-content: center;
    flex-wrap: nowrap;
  }

  .key {
    flex: 0 0 9%;
    height: 36px;
    line-height: 36px;
    font-size: 14px;
    margin: 1px;
    box-sizing: border-box;
  }
}

@media (max-width: 400px) {
  #keyboard {
    width: 100%;
    padding: 0;
  }

  .keyboard-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(0, 1fr));
    gap: 2px;
    width: 100%;
  }

  .key {
    margin: 0; /* remove margin, use grid gap */
    height: 36px;
    line-height: 36px;
    font-size: 14px;
    text-align: center;
    box-sizing: border-box;
    cursor: pointer;
  }
}