*{
  box-sizing: border-box;
  font-family: Arial, sans-serif;
}

body{
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: #f2f2f2;
}

.calculator{
  width: 320px;
  background: #222;
  padding: 15px;
  border-radius: 10px;
}

.screen{
  background: #000;
  color: #fff;
  padding: 10px;
  text-align: right;
  border-radius: 5px;
}

.answer{
  font-size: 28px;
  margin-bottom: 5px;
}

.numbers{
  font-size: 16px;
  color: #bbb;
  margin-bottom: 15px;
}

.buttons{
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.buttons > .c-btn{
  background-color: red;
  color: white;
}
button{
  width: 65px;
  height: 50px;
  border: none;
  border-radius: 5px;
  font-size: 18px;
  cursor: pointer;
}

button:hover{
  background: #ddd;
}

.equal{
  background: orange;
  color: #fff;
}

.zero{
  width: 140px;
}