body {
  background: #f0f0f0;
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.calculator {
  max-width: 100%;
  width: 100%;
  max-width: 520px;
  margin: 30px auto;
  padding: 20px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.3);
  font-weight: bold;
  box-sizing: border-box;
  overflow-x: auto;
}

#display {
  width: 100%;
  height: 80px;
  font-size: 28px;
  font-weight: bold;
  text-align: right;
  padding: 20px;
  margin-bottom: 20px;
  border: 2px solid #ccc;
  border-radius: 8px;
  background: white;
  color: black;
  box-sizing: border-box;
}

.buttons, .scientific {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
}

.scientific {
  display: none;
  margin-bottom: 20px;
}

button {
  padding: 15px;
  font-size: 16px;
  font-weight: bold;
  border-radius: 8px;
  border: 1px solid #ccc;
  background: #e6e6e6;
  color: black;
  cursor: pointer;
  box-shadow: 2px 2px 4px #bbb inset;
  transition: background 0.2s, transform 0.1s;
}

button:hover {
  background: #dcdcdc;
  transform: scale(1.02);
}

button:active {
  background: #cfcfcf;
  box-shadow: inset 1px 1px 3px #999;
}