style.css

*,
*::before,
*::after {
  box-sizing: border-box;
}
/* Remove default margin, padding and fix font */
* {
  margin: 0;
  padding: 0;
  font: inherit;
}

/*
  Typographic tweaks!
  Add accessible line-height
  Improve text rendering
*/
body {
  line-height: 1.5;
}

:root {
  --clr-primary-100: rgb(228, 226, 226);
  --clr-primary-300: rgb(184, 183, 183);
  --clr-primary-400: rgb(151, 151, 151);
  --clr-primary-500: rgb(128, 128, 128);
  --clr-primary-700: rgb(56, 56, 56);
  --clr-alternate-400: rgb(255, 187, 0);

  --fs-300: 3rem;
  --fs-600: 6rem;
}

#calculator {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  width: 50rem;
  height: 70rem;
  margin: 5rem auto 0 auto;
  gap: 0.5rem;
  background-color: var(--clr-primary-700);
  padding: 1.5rem;
}

#displayBar {
  grid-column: 1 / 5;
  font-size: var(--fs-600);
  text-align: right;
  background-color: var(--clr-primary-100);
  padding: 1rem;
  overflow: hidden;
  text-overflow: ellipsis;
}

.bigButton {
  grid-column: 1 / 3;
}

button {
  background-color: var(--clr-primary-400);
  border: var(--clr-primary-500);
  font-size: var(--fs-300);
}

#displayBar,
#calculator,
button {
  border-radius: 1.5rem;
}

.clr-orange {
  background-color: var(--clr-alternate-400);
}

.clr-lgrey {
  background-color: var(--clr-primary-300);
}

button:hover {
  filter: brightness(0.9);
}

button:active {
  filter: brightness(0.7);
}