style.css

* {
  padding: 0;
  margin: 0;
}

html {
  font-family: sans-serif;
  text-align: center;
}

.main {
  display: flex;
  justify-content: center;
  align-items: center;
  align-content: center;
  background-color: beige;
  min-height: 95vh;
  overflow: hidden;
  height: 100vh;
}

.container {
  width: 25rem;
  height: 30rem;
  max-width: 500px;
  background-color: #1c1c1c;
  border-radius: 10px;
  display: grid;
  justify-content: center;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(6, 1fr);
  gap: 5px;
  padding: 2rem;
  transform: perspective(55em) rotateX(58deg) rotateY(0deg) rotateZ(-40deg);
  transform-style: preserve-3d;
  border-radius: 33px;
  box-shadow: -4px 4px 0 1px #f9f9fb, 1px 0 30px 0 rgba(34, 33, 81, 0.01),
    -30px 28px 28px 0 rgba(34, 33, 81, 0.25);
}
.container:hover {
  transform: perspective(75em) rotateX(0);
  box-shadow: 0 0 0 0 #f9f9fb, 1px 0 30px 0 rgba(34, 33, 81, 0.01),
    -1px 1px 12px 0 rgba(34, 33, 81, 0.25);
}

.displayArea {
  grid-column-start: 1;
  grid-column-end: 5;
  background-color: inherit;
  /* border: 3px solid black; */
  margin: 2px 0;
  padding-right: 1rem;
  font-size: 4rem;
  text-align: right;
  color: #fff;
  max-width: 400px;
  min-height: 3rem;
  overflow: hidden;
  text-overflow: ellipsis;
}
.btn-double {
  grid-column-end: 3;
  grid-column-start: 1;
}
.btn {
  margin: 1.5px;
  justify-content: center;
  border-radius: 8px;
  font-size: 2rem;
  border: none;
  cursor: pointer;
}
.btn-orange {
  color: #fff;
  font-size: 3rem;
  background: linear-gradient(to right, #ff9500, #fa960a);
}
.btn-orange:active {
  background-color: #f0a132;
}
.btn-orange:hover {
  background: linear-gradient(to right, #f9960c, #f6ae4a);
}

.btn-gray {
  background: linear-gradient(to right, #c8c8c7, #999999);
}
.btn-gray:active {
  background-color: #f0f0ee;
}
.btn-gray:hover {
  background: linear-gradient(to right, #dadad9, #aeaeae);
}

.btn-dark {
  background: linear-gradient(to right, #5d5d5d, #505050);
  color: #fff;
}
.btn-dark:active {
  background-color: #6c6c6c;
}
.btn-dark:hover {
  background: linear-gradient(to right, #707070, #646464);
}