style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Verdana, Tahoma, sans-serif;
}

body {
  height: 100vh;
  background: linear-gradient(135deg, #764ba2, #667eea);
  display: flex;
  justify-content: center;
  align-items: center;
}

.calculator {
  width: 320px;
  background: #222;
  border-radius: 10px;
  padding: 15px;
}

#display {
  width: 100%;
  height: 60px;
  background: #000;
  color: #0f0;
  font-size: 2rem;
  text-align: right;
  padding: 10px;
  border: none;
  margin-bottom: 10px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

button {
  padding: 15px;
  font-size: 1.2rem;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

button:hover {
  opacity: 0.8;
}

.operator {
  background: #ff9f43;
}

.equal {
  background: #1dd1a1;
  grid-row: span 2;
}

.clear {
  background: #ee5253;
}

.delete {
  background: #576574;
}

.zero {
  grid-column: span 2;
}

button:not(.operator):not(.equal):not(.clear):not(.delete) {
  background: #c8d6e5;
}