* {
  box-sizing: border-box;
  font-family: system-ui, -apple-system, BlinkMacSystemFont;
}

body {
  min-height: 100vh;
  margin: 0;
  background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
  display: flex;
  align-items: center;
  justify-content: center;
}

.calculator {
  backdrop-filter: blur(16px);
  background: rgba(255, 255, 255, 0.12);
  border-radius: 20px;
  padding: 20px;
  width: 320px;
  box-shadow: 0 20px 40px rgba(0,0,0,0.3);
}

.display {
  background: rgba(0,0,0,0.35);
  color: #fff;
  font-size: 2.2rem;
  padding: 15px;
  border-radius: 12px;
  text-align: right;
  margin-bottom: 15px;
  overflow-x: auto;
}

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

button {
  background: rgba(255,255,255,0.18);
  border: none;
  border-radius: 12px;
  padding: 15px;
  font-size: 1.2rem;
  color: #fff;
  cursor: pointer;
  transition: transform 0.1s, background 0.2s;
}

button:hover {
  background: rgba(255,255,255,0.3);
}

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

.equal {
  grid-row: span 2;
  background: #4ade80;
  color: #000;
}

.zero {
  grid-column: span 2;
}