style.css

@import url("https://fonts.googleapis.com/css2?family=Quicksand:wght@300&display=swap");
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Quicksand", sans-serif;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: #091921;
}
body::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(#1ea2e9, #ff0707);
  clip-path: circle(15% at 30% 20%);
}
body::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(#fff, rgb(0, 255, 191));
  clip-path: circle(15% at 70% 90%);
}
.container {
  position: relative;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 6px;
  overflow: hidden;
  z-index: 10;
}
.container .calculator {
  position: relative;
  display: grid;
}
.container .calculator .value {
  grid-column: span 4;
  width: 300px;
  height: 140px;
  text-align: right;
  outline: none;
  border: none;
  padding: 10px;
  font-size: 30px;
  color: #fff;
  background: transparent;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  border-right: 1px solid rgba(255, 255, 255, 0.05);
}
.container .calculator span {
  display: grid;
  place-items: center;
  width: 75px;
  height: 75px;
  color: #fff;
  font-weight: 400;
  cursor: pointer;
  font-size: 20px;
  user-select: none;
  transition: 0.5s;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  border-right: 1px solid rgba(255, 255, 255, 0.05);
}
.container .calculator span:hover {
  transition: 0s;
  background: rgba(255, 255, 255, 0.05);
}
.container .calculator span:active {
  background: #14ff47;
  color: #192f00;
  font-size: 24px;
  font-weight: 500;
}
.container .calculator .clear {
  grid-column: span 2;
  width: 150px;
  background: rgba(255, 255, 255, 0.05);
}
.container .calculator .plus {
  grid-row: span 2;
  height: 150px;
}
.equal {
  background: rgba(255, 255, 255, 0.05);
}