style.css

:root {
  --primary-color: #0088cc;
  --secondary-color: #004e7a;
  --third-color: #c30000;
}

.calculator {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 10px;
  padding: 10px;
  background-color: #dddddd;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.2);
}

.calculator button {
  padding: 20px;
  font-size: 32px;
  border: none;
  background-color: #fff;
  color: var(--primary-color);
  border-radius: 10px;
  cursor: pointer;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
  transition: background-color 0.2s ease-in-out;
}

.calculator button:hover {
  background-color: #eee;
}

.calculator button:active {
  box-shadow: none;
}

.calculator input[type="text"] {
  grid-column: 1 / span 4;
  padding: 20px;
  font-size: 32px;
  text-align: right;
  border: 5px;
  background-color: #ffffff;
  color: var(--secondary-color);
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

.calculator button:nth-child(16) {
  background-color: var(--secondary-color);
  color: #fff;
}

.calculator button:nth-child(19) {
  background-color: #00dd99;
  color: #fff;
}
.calculator button:nth-child(18) {
  background-color: var(--third-color);
  color: #fff;
}

.calculator button:nth-child(17) {
  background-color: var(--primary-color);
  color: #fff;
}

.calculator button:nth-child(13) {
  background-color: var(--primary-color);
  color: #fff;
}

.calculator button:nth-child(9) {
  background-color: var(--primary-color);
  color: #fff;
}

.calculator button:nth-child(5) {
  background-color: var(--primary-color);
  color: #fff;
}