body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: 0;
  background-color: rgb(66, 60, 60);
  font-family: Arial;
}

.calculator {
  background: white;
  border-radius: 20px;
  width: 420px;
  height: 520px;
  box-shadow: 0px 10px 15px rgba(0, 0, 0, 0.2);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 20px;
}

.input {
  background-color: #786e6e;
  color: #ffffff;
  font-size: 30px;
  text-align: right;
  border-radius: 15px;
  border: 2px solid #444444;
  margin-bottom: 20px;
  height: 700px;
  width: 100%;
  box-shadow: inset 0px 4px 6px rgba(0, 0, 0, 0.2);
}

.keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.keys button {
  background-color: #555555;
  color: #fff;
  font-size: 20px;
  padding: 20px;
  border-radius: 12px;
  border: none;
  cursor: pointer;
  transition: background-color 0.3s, transform 0.1s ease-in-out;
  box-shadow: 0px 4px 8px rgba(0, 0, 0, 0.2);
}

.keys button:hover {
  background-color: #ff6f00;
  transform: scale(1.05);
}

.keys button:active{
  opacity: 0.5;
}

.keys button.operator {
  background-color: #ff6f00;
}

.keys button.operator:hover {
  background-color: #ff8f1a;
}

.keys button.equal {
  background-color: #00c853;
}

.keys button.equal:hover {
  background-color: #1de9b6;
}

.keys button.clear {
  background-color: #d32f2f;
}

.keys button.clear:hover {
  background-color: #f44336;
}