* {
  box-sizing: border-box;
  font-family: "Segoe UI", system-ui, sans-serif;
}

body {
  background: #eaf2ff;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.calculator {
  background: #f7fbff;
  width: 320px;
  border-radius: 20px;
  padding: 20px;
  box-shadow: 0 20px 40px rgba(0, 40, 120, 0.15);
}

.title {
  text-align: center;
  font-size: 22px;
  font-weight: 600;
  color: #2f5fa7;
  margin-bottom: 12px;
}

.display {
  background: #dceaff;
  height: 60px;
  border-radius: 12px;
  padding: 10px;
  font-size: 26px;
  text-align: right;
  color: #183a6d;
  overflow-x: auto;
  margin-bottom: 16px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

button {
  height: 55px;
  border-radius: 14px;
  border: none;
  font-size: 18px;
  cursor: pointer;
  background: #edf4ff;
  color: #2a4f87;
  box-shadow: 0 6px 12px rgba(0, 60, 150, 0.15);
}

button:active {
  transform: scale(0.96);
}

.operator {
  background: #c9dcff;
  color: #123c75;
}

.clear {
  background: #ffd6d6;
  color: #7a1f1f;
}

.equal {
  grid-column: span 2;
  background: #2f5fa7;
  color: white;
}