styles.css

body {
  margin: 20vh 1rem 20vh 1rem;
  text-align: center;
}

#calculator {
  background-color: darkslategray;
  height: 100%;
  display: inline-grid;
  border-radius: 20px;
  padding: 40px 15px 25px 15px;
  justify-content: center;
  align-self: center;

  grid-gap: 0.5rem;
  grid-template-columns: 40px 40px 40px 40px 40px;
  grid-template-rows: 40px 40px 40px 40px 40px;
  grid-template-areas:
    "header header header header header"
    ". . . . ."
    ". . . . ."
    "eq . . . ."
    "eq . . . .";
}

#display {
  grid-area: header;
  background-color: darkseagreen;
  font-size: 30px;
  font-family: consolas;
  text-align: left;
  white-space: nowrap;
  align-self: center;
  overflow-x: auto;
  scroll-behavior: auto;
  padding: 5px 10px 5px 10px;
  margin-bottom: 50px;
  border-radius: 5px;
  box-shadow: inset 1px 1px 1px 1px #000;
}
button {
  font-size: 24px;
  font-family: consolas;
  border-radius: 3px;
  outline: none;
}

.operator {
  background-color: silver;
}

#C {
  background-color: lightcoral;
}

#CE {
  background-color: lightcoral;
}
#eq {
  grid-area: eq;
  background-color: skyblue;
}