.button {
  margin-bottom: 10px;
  background-color: rgba(0, 0, 0, 0.1);
  padding: 10px;
  color: #fff;
  cursor: pointer;
  width: 120px;
}

.rectangle {
  width: 100%;
  height: calc(100% - 50px);
  --start: hsl(0, 100%, 50%);
  --end: hsl(322, 100%, 50%);
  background-image: linear-gradient(-135deg, var(--start), var(--end));
}