style.css

body {
  height: 100vh;
  background-image: linear-gradient(to bottom right, #74c0fc, #38d9a9);
  background-repeat: no-repeat;
  overflow: hidden;
}
.main {
  margin: 12% auto;
  width: 50%;
  display: flex;
  flex-direction: column;
  row-gap: 16px;
  align-items: center;
  background-color: rgba(153, 153, 153, 0.37);
  border-radius: 22px;
}
.btn {
  width: 150px;
  height: 100px;
  border-radius: 10px;
  padding: 30px;
  transition: ease-in;
  transition-duration: 250ms;
  border-width: 2px;
  border-color: black;
}
.btns {
  display: grid;
  grid-template-columns: 100px 100px;
  row-gap: 10px;
  column-gap: 60px;
  align-items: center;
  justify-items: center;
}
.btn:hover {
  transform: scale(105%);
}
.redC {
  background-color: #ff0000;
}
.greC {
  background-color: #008000;
}
.bluC {
  background-color: #0000ff;
}
.yelC {
  background-color: #ffff00;
}
.heading {
  font-size: 28px;
  font-family: monospace;
}
.score {
  font-size: 36px;
  padding-top: 50px;
  font-family: monospace;
}
.greyed {
  background-color: #555555;
}