html {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #333333;  /* fallback for old browsers */
  background: -webkit-linear-gradient(to right, #dd1818, #333333);  /* Chrome 10-25, Safari 5.1-6 */
  background: linear-gradient(to left, #dd1818, #333333); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
  } 

  .calculator{
    background: white;
    width: 400px;
    border-radius: 12px;
    box-shadow: 0 5px 30px -5px rgba(255, 255, 255, 0.6);
  }

  .calculator-display{
    background-color: black;
    color: white;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    margin: 0;
    border-radius: 10px 10px 0 0;
  }

  .calculator-display h1 {
    margin: 0;
    padding: 25px;
    font-size: 45px;
    font-family: 'Lucida Console', sans-serif;
    font-weight: 100;
    overflow-x: auto;
  }

  /* Custom ScrollBar */
  ::-webkit-scrollbar {
    width: 10px;
  }
  
  ::-webkit-scrollbar-track {
    background: #f1f1f1;
  }
  
  ::-webkit-scrollbar-thumb {
    background: #888;
  }
  
  ::-webkit-scrollbar-thumb:hover {
    background: #555;
  }

  /* Buttons */
  .calculator-buttons{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 10px;
  }

  button{
    min-height: 50px;
    font-size: 20px;
    font-weight: 100;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    background-color: rgb(175, 173, 173);
  }

  button:hover{
    filter: brightness(120%);
  }

  button:active{
    transform: translateY(1px);
  }

  button:focus{
    outline: none;
  }

  .operator {
    background-color: orange;
    font-size: 35px;
  }

  .clear{
    background: rgb(251 46 46);
    color: white;
  }

  .equals-sign{
    grid-column: -2;
    grid-row: 2 / span 4;
    background: #333333;
    color: white;
  }


@media screen and (width < 600px){
  .calculator{
    width: 95%;
  }
}