style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'poppins', sans-serif;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #518bea;
  background-image: radial-gradient(at 47% 33%, hsl(133.90, 88%, 64%) 0, transparent 59%),
    radial-gradient(at 82% 65%, hsl(50.81, 82%, 73%) 0, transparent 55%);
  background-attachment: fixed;
}

body::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(to right, #e91e63, #ffc107);
  clip-path: circle(12% at 60% 10%);
}

body::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(#ffffff, #da00ff);
  clip-path: circle(8% at 40% 60%);
}

.container {
  background-color: rgba(38, 56, 84, 0.3);
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.125);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  position: relative;
  overflow: hidden;
  z-index: 10;
}

.calculator {
  display: grid;
  justify-content: center;
  align-items: center;
  grid-template-columns: repeat(4, 75px);
  grid-template-rows: minmax(150px, auto) repeat(5, 75px);

}

.calculator button {
  height: 75px;
  cursor: pointer;
  font-size: 1.6rem;
  border: 1px solid rgba(255, 255, 255, 0.07);
  color: #fff;
  outline: none;
  background-color: rgba(20, 29, 43, 0);
  transition: 0.5s;
}

.calculator button:hover {
  background-color: rgba(255, 255, 255, .1);
  transition: 0s;
}

.calculator .clear {
  grid-column: span 2;
}

.calculator .plus {
  grid-row: span 2;
  height: 150px;
}

.output {
  grid-column: 1/-1;
  display: flex;
  align-items: flex-end;
  justify-content: space-around;
  flex-direction: column;
  padding: 10px;
  word-wrap: break-word;
  word-break: break-all;
}

.previous-operand {
  color: rgba(255, 255, 255, 0.8);
  font-size: 1.3rem;
}

.current-operand {
  color: #fff;
  font-size: 2rem;
}