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

body {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #f0f0f0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

.calculator {
  background: #fff;
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 16px;
  width: 100%;
  max-width: 320px;
}

.display {
  background: #fff;
  border: 1px solid #ddd;
  border-radius: 4px;
  padding: 16px;
  font-size: 2rem;
  text-align: right;
  margin-bottom: 12px;
  min-height: 60px;
  overflow-x: auto;
}

.keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}

.key {
  border: 1px solid #ccc;
  border-radius: 4px;
  padding: 14px 0;
  font-size: 1.1rem;
  cursor: pointer;
  background: #f9f9f9;
  transition: background 0.1s;
}

.key:hover { background: #e9e9e9; }
.key:active { background: #ddd; }

.key.clear { background: #ff5252; color: #fff; border-color: #ff5252; }
.key.clear:hover { background: #ff7373; }

.key.func { background: #e0e0e0; }
.key.func:hover { background: #d5d5d5; }

.key.op { background: #ff9800; color: #fff; border-color: #ff9800; }
.key.op:hover { background: #ffab2e; }

.key.equals { background: #2196f3; color: #fff; border-color: #2196f3; }
.key.equals:hover { background: #4da6ff; }

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