style.css

@import url("https://fonts.googleapis.com/css2?family=Roboto:wght@400;500;700&family=Rubik:wght@400;500;600;700;800&display=swap");

*,
*::before,
*::after {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

html {
  font-size: 62.5%;
}

body {
  font-family: "Roboto", sans-serif;
  font-weight: 400;
  line-height: 1;
  color: 1;
}

.calculator {
  width: 60rem;
  margin: 5rem auto;

  display: grid;
  grid-template-columns: repeat(4, 1fr);
  border-radius: 4px;
  overflow: hidden;
}

button {
  border: none;
  outline: none;
  padding: 2.4rem 6.4rem;
  border: 1px solid #ddd;
  cursor: pointer;
  font-size: 2rem;
  /* border-collapse: collapse; */
}

.btn-equal {
  grid-column: 3 / span 2;
  background-color: #7048e8;
  color: #fff;
  font-size: 3.2rem;
}

.btn-clear,
.btn-clearOne {
  background-color: #7048e8;
  color: #fff;
}

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

.btn-operation {
  font-size: 2.4rem;
  color: #343a40;
}

.prevEl,
.currentEl {
  height: 5rem;
  grid-column: 1/-1;
  display: flex;
  flex-direction: row-reverse;
  align-items: center;
  font-size: 2rem;
  padding: 3.2rem 1.8rem;
}

.currentEl {
  background-color: #cbeee5;
  font-size: 3.2rem;
}

.prevEl {
  background-color: #edf2ff;
}