styles.css

html {
  display: flex;
  height: 100%;
  align-items: center;
  justify-content: center;
  margin: 0;
  padding: 0;
  background-color: #181818;
}

main-calculator-container {
  display: flex;
  width: 60vw;
  align-items: center;
  justify-content: center;
  width: 100%;
  margin: 100px;
}

#equalsButton {
  grid-column: 1 / span 3;
  font-size: 3rem;
  color: #2db6fa;
  background-color: #3d3d3d;
}

#displayHistory {
  margin-top: 20px;
  font-size: 1.5rem;
  grid-column: 1 / span 3;
  height: 80%;
  font-size: 3rem;
  color: #2db6fa;
  background-color: #212121;
}

#mainDisplay {
  padding: 0;
  margin: 0;
  grid-column: 1 / span 3;
  margin: 0;
  height: 80%;
  font-size: 3rem;
  width: 100%;
  color: #2db6fa;
  background-color: #212121;
  border: none !important;
  box-shadow: none !important;
  outline: none !important;
}

.main-buttons-container {
  height: 80vh;
  row-gap: 20px;
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
}

.calcButton,
#deleteButton {
  background-color: #3d3d3d;
  color: #2db6fa;
  font-size: 3rem;
  padding: 0;
  margin: 0;
  width: 100%;
}

#displayHistory::-webkit-scrollbar-track {
  -webkit-box-shadow: inset 0 0 6px 3d3d3d;
  background-color: #3d3d3d;
}

#displayHistory::-webkit-scrollbar {
  width: 10px;
  background-color: #3d3d3d;
}

#displayHistory::-webkit-scrollbar-thumb {
  background-color: #2db6fa;
  background-image: -webkit-linear-gradient(
    45deg,
    rgba(255, 255, 255, 0.2) 25%,
    transparent 25%,
    transparent 50%,
    rgba(255, 255, 255, 0.2) 50%,
    rgba(255, 255, 255, 0.2) 75%,
    transparent 75%,
    transparent
  );
}