body {
  background: #f7f9fc;
  font-family: 'Segoe UI', sans-serif;
  display: flex;
  justify-content: center;
  padding: 2rem;
  margin: 0;
}
.calculator-wrapper {
  background: white;
  border-radius: 16px;
  padding: 2rem;
  max-width: 400px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}
h1 {
  text-align: center;
  margin-bottom: 1rem;
}
#display {
  width: 100%;
  font-size: 1.5rem;
  padding: 0.75rem;
  margin-bottom: 1rem;
  text-align: right;
  border: 1px solid #ccc;
  border-radius: 8px;
}
.button-panel {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
}
.button-panel button {
  padding: 1rem;
  font-size: 1.25rem;
  border: none;
  border-radius: 8px;
  background: #e0e0e0;
  cursor: pointer;
}
.button-panel button:hover {
  background: #d1d1d1;
}
.equal {
  background: #4caf50;
  color: white;
}
.equal:hover {
  background: #45a049;
}
#clear {
  background: #f44336;
  color: white;
}
#clear:hover {
  background: #e53935;
}
.history-panel {
  margin-top: 2rem;
}
.history-panel h2 {
  font-size: 1.2rem;
  margin-bottom: 0.5rem;
}
.history-panel ul {
  list-style: none;
  padding: 0;
}
.history-panel li {
  font-size: 0.9rem;
  border-bottom: 1px solid #ddd;
  padding: 0.3rem 0;
}