@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

body {
  font-family: 'Inter', sans-serif;
  background-color: #f3f4f6;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.calculator-container {
  width: 100%;
  max-width: 28rem;
  background-color: white;
  border-radius: 1rem;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  overflow: hidden;
  transition: all 0.3s ease;
}

.calculator-content {
  padding: 1.5rem;
}

.display {
  background-color: #f9fafb;
  border-radius: 0.75rem;
  padding: 1rem;
  text-align: right;
  margin-bottom: 1.5rem;
  min-height: 6.25rem;
}

#previous-operand {
  color: #6b7280;
  font-size: 1.125rem;
  height: 1.5rem;
}

#current-operand {
  font-size: 1.875rem;
  font-weight: 600;
}

.buttons-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.75rem;
}

button {
  border: none;
  font-weight: 500;
  padding: 0.75rem 0;
  border-radius: 0.5rem;
  cursor: pointer;
  transition: all 0.2s ease;
}

button:active {
  transform: scale(0.95);
}

.number {
  background-color: #f3f4f6;
  color: #111827;
}

.number:hover {
  background-color: #e5e7eb;
}

.operation {
  font-weight: 700;
}

.operation.secondary {
  background-color: #e0f2fe;
  color: #0369a1;
}

.operation.secondary:hover {
  background-color: #0ea5e9;
  color: white;
}

.operation.primary {
  background-color: #d1fae5;
  color: #047857;
}

.operation.primary:hover {
  background-color: #10b981;
  color: white;
}

.equals {
  background-color: #10b981;
  color: white;
  font-weight: 700;
  grid-row: span 2;
}

.equals:hover {
  background-color: #047857;
}

.span-2 {
  grid-column: span 2;
}

/* Animation for button presses */
@keyframes buttonPress {
  0% { transform: scale(1); }
  50% { transform: scale(0.95); }
  100% { transform: scale(1); }
}

button.active {
  animation: buttonPress 0.2s ease;
}