calc.css

html {
    box-sizing: border-box;
    font-size: 175%;
    font-weight: 100;
    line-height: 1.3;
  }
body {
    align-items: center;
    background-image: linear-gradient(150deg, #da4a9e, #37a9eb);
    display: flex;
    height: 100vh;
    justify-content: center;
    font-family: monospace;
  }

input,
textarea,
button, .calculator .calculator_display {
  border: 0;
  border-radius: 25;
  background-color: #aaa6a646;
  font-size: inherit;
  font-family: inherit;
  font-weight: inherit;
  outline: none;
  text-align: left;
  padding: 1rem;
}

  .container {
      display: grid; 
      font-size: 1em;
  }

  .calculator {
    border: 2px solid #37a9eb;
    padding: 0px; 
    background: #aaa6a646;
    width: 13em; 
    position: relative;
  }
  
  *,
  *::before,
  *::after {
    box-sizing: inherit;
  }
  
  body {
    margin: 0;
  }
  
  /* input:hover,
  input:active,
  input:focus,
  textarea:hover,
  textarea:active,
  textarea:focus,
  button:hover,
  button:active,
  button:focus {
    outline: none;
  } */
  
  .container {
    max-width: 30em;
  }
  
  .container > p {
    text-align: center;
  }
  
  .calculator {
    border-radius: 12px;
    box-shadow: 0 0 40px 0px rgba(0, 0, 0, 0.15);
    margin-left: auto;
    margin-right: auto;
    margin-top: 2em;
    max-width: 30em;
    overflow: hidden;
  }
  
  .calculator_display {
    background-color: #222222;
    color: #936aa0;
    font-size: 1.714285714em;
    padding: 0.5em 0.75em;
    text-align: right;
  }
  
  .calculator_keys {
    background-color: #999;
    display: grid;
    grid-gap: 1px;
    grid-template-columns: repeat(4, 1fr);
  }
  
  .calculator_keys > * {
    background-color: #fff;
    padding: 0.5em 1em;
    position: relative;
    text-align: center;
  }
  
  .calculator_keys > *:active::before,
  .calculator_keys > .is-depressed::before {
    background-color: rgba(0, 0, 0, 0.2);
    bottom: 0;
    box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.8) inset;
    content: "";
    left: 0;
    opacity: 0.3;
    position: absolute;
    right: 0;
    top: 0;
    z-index: 1;
  }
  
  .key-operator {
    background-color: #eee;
  }
  
  .key-equal {
    background-image: linear-gradient(to bottom, #d252f1, #680f51);
    grid-column: -2;
    grid-row: 2 / span 4;
  }