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

body {
  font-family: Arial, sans-serif;
  background-color: #f0f0f0;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.main {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.calculator {
  background-color: #fff;
  border-radius: 8px;
  box-shadow: 0px 4px 8px rgba(0, 0, 0, 0.1);
  padding: 20px;
  text-align: center;
}

#result {
  width: 100%;
  height: 50px;
  font-size: 30px;
  border: none;
  outline: none;
  margin-bottom: 10px;
  padding: 10px;
}

button {
  width: 80px;
  height: 80px;
  font-size: 24px;
  border: none;
  background-color: #f2f2f2;
  color: #333;
  cursor: pointer;
  transition: background-color 0.2s;
  margin: 5px;
  border-radius: 4px;
}

.operator {
  background-color: #444;
  color: #fff;
}

.equals {
  background-color: #666;
  color: #fff;
}

.clear {
  background-color: #e84d4d;
  color: #fff;
}

button:hover {
  background-color: #d0d0d0;
}

.footer {
  font-size: 12px;
  color: #888;
  margin-top: 20px;
}