ocean.css

*{
    background-color: deepskyblue;
}

.calculator {
    border: 4px solid darkcyan;
    width: 300px;
    margin: 50px auto;
    padding: 10px;
    background-color: deepskyblue;
    border-radius: 5px;
  }
  .display {
    width: 100%;
    margin-bottom: 10px;
    background-color: deepskyblue;
    border: 2px solid darkcyan;
    border-radius: 4px;
  }
  .display input[type="text"] {
    color: darkblue;
    width: auto;
    padding: 10px;
    font-size: 20px;
    text-align: right;
    border: none;
    outline: none;
  }
  .buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 5px;
  }
  button {
    background-color: deepskyblue;
    color: beige;
    padding: 10px;
    border: 1px solid darkcyan;
    border-radius: 4px;
    cursor: pointer;
  }
  button:hover {
    background-color: blue;
  }
  
  button:active{
    background-color: darkblue;
  }
  
  .themes{
    align-items: center;
    display: flex;
    justify-content: center;
  }

  .themes > button{
    border: blue;
    margin:2px;
    background-color: aquamarine;
    color: blue;
  }