body {
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

#calculator {
 background: #2c3e50;
 border-radius: 20px;
 padding: 20px;
 box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

#container {
  display: grid;
  grid-template-columns: repeat(4, 100px);
  grid-template-rows: minmax(100px, auto) repeat(5, 80px);
  gap: 10px ;
  justify-items: stretch;
  justify-content: center;
  grid-auto-flow: row;
}

#display {
  grid-column: 1 / -1;
  background-color: #000;
  color: #fff;
  font-size: 50px;
  padding: 20px;
  text-align: right;
  border-radius: 10px;
  margin-bottom: 15px;
  min-height: 50px;
}

button {
  padding: 20px;
  font-size: 1.2em;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.2s;
  font-weight: bold;
}

button:hover {
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.clear {
  grid-column: span 2;
}

.zero {
  grid-column: span 2;
}