style.css

body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  background-image: url('https://images.unsplash.com/photo-1506744038136-46273834b3fb');
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}

* {
  box-sizing: border-box;
  outline: none;
}

.container {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.calculator {
  background-color: rgba(255, 255, 255, 0.2);
  padding: 15px;
  border-radius: 30px;
  box-shadow: inset 5px 5px 12px #3f8de7, 5px 5px 12px rgba(89, 223, 56, 0.826);
  display: grid;
  grid-template-columns: repeat(4, 68px);
}

input {
  grid-column: span 4;
  height: 70px;
  width: 260px;
  background-color: rgba(255, 255, 255, 0.2);
  box-shadow: inset -5px -5px 12px #3f8de7, inset 5px 5px 12px rgba(89, 223, 56, 0.826);
  border: none;
  border-radius: 30px;
  color: rgb(187, 16, 16);
  font-size: 50px;
  text-align: end;
  margin-top: 40px;
  margin-bottom: 30px;
  padding: 20px;
}

button {
  height: 48px;
  width: 48px;
  background-color: rgba(255, 255, 255, 0.2);
  box-shadow: -5px -5px 12px #3f8de7, 5px 5px 12px rgba(89, 223, 56, 0.826);
  border: none;
  border-radius: 50%;
  margin: 8px;
  font-size: 16px;
  font-weight: bold;
}

.equal {
  width: 115px;
  border-radius: 40px;
  background-color: rgba(255, 255, 255, 0.2);
  box-shadow: -5px -5px 12px #3f8de7, 5px 5px 12px rgba(89, 223, 56, 0.826);
}