* {
  margin: 0;
  padding: 0;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  background-color: #e9e9e9;
  font-family: monospace, sans-serif;
  font-size: 24px;
}

body {
  height: 100vh;
  width: 100vw;
  display: flex;
  align-items: center;
  justify-content: center;
}

.wrapper {
  box-shadow: -6px -6px 9px #fff, 6px 6px 9px rgba(0, 0, 0, 0.4);
  padding: 20px;
  border-radius: 30px;
}

.wrapper input {
  outline: none;
}

.wrapper #input {
  box-shadow: inset -6px -6px 9px #fff, inset 6px 6px 9px rgba(0, 0, 0, 0.4);
  width: 320px;
  height: 60px;
  padding: 16px 32px;
  text-align: right;
  border: none;
  border-radius: 30px;
  text-shadow: -1px -1px 2px #fff, 2px 2px 2px rgba(0, 0, 0, 0.4);
}

.wrapper .keys {
  display: -ms-grid;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 5px;
  margin-top: 20px;
}

.wrapper input {
  box-shadow: -6px -6px 9px #fff, 6px 6px 9px rgba(0, 0, 0, 0.4);
  width: 60px;
  height: 60px;
  border: none;
  border-radius: 50%;
  margin-top: 5px;
  cursor: pointer;
  background: #e9e9e9;
}

.wrapper input:hover,
.wrapper input:active {
  background-color: #ccc;
}

.wrapper input:active {
  box-shadow: inset -6px -6px 9px #fff, inset 6px 6px 9px rgba(0, 0, 0, 0.4);
}

.wrapper .operator-key,
.wrapper .equal-key {
  color: #ff652f;
}