* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  width: 100%;
  background: linear-gradient(135deg, #6495ED 0%, #764ba2 100%);
  font-family: 'Segoe UI', Tahoma, sans-serif;
}

.calculator {
  background: #2c3e50;
  border-radius: 20px;
  margin: 25px 0;
  padding: 25px;
  box-shadow: 0 12px 24px rgba(0, 0, 0, .3);
  width: 320px;
}

.display {
  margin-bottom: 20px;
}

#result {
  width: 100%;
  height: 80px;
  background: #34495e;
  border: none;
  border-radius: 10px;
  color: white;
  font-size: 2.5rem;
  text-align: right;
  padding: 0 20px;
  outline: none;
  box-shadow: inset 0 4px 8px rgba(0, 0, 0, .2);
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 15px;
}

button {
  height: 60px;
  border: none;
  border-radius: 10px;
  background: #3498db;
  color: white;
  font-size: 1.5rem;
  font-weight: bold;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

button:hover {
  background: #2980b9;
  transform: translateY(-2px);
}

button:active {
  transform: translateY(0);
}

.equals {
  background: #e74c3c;
  grid-column: span 2;
}

.equals:hover {
  background: #c0392b;
}

button:nth-child(1),
button:nth-child(2),
button:nth-child(3),
button:nth-child(4) {
  background: #95a5a6;
}

button:nth-child(1):hover,
button:nth-child(2):hover,
button:nth-child(3):hover,
button:nth-child(4):hover {
  background: #7f8c8d;
}