style.css

*{
  margin:0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins' , sans-serif;
}
body{
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: linear-gradient(45deg,#0a0a0a,#3a4452);
}

.cal{
  border: 1px solid #717377;
  border-radius: 16px;
  padding: 20px;
  background: transparent;
  box-shadow: 0px 3px 15px rgba(113,115,119,0.5);
}

input{
  width: 320px;
  border: none;
  padding: 24px;
  margin: 10px;
  background: transparent;
  box-shadow: 0px 3px 15px rgba(84,84,84,0.1);
  font-size: 40px;
  text-align: right;
  cursor: pointer;
  color: #ffffff;
}

input::placeholder{
  color: #ffffff;

}

button{
  border:none;
  width:60px;
  height:60px;
  margin:10px;
  border-radius:50px;
  background: transparent;
  color: #ffffff;
  font-size: 20px;
  box-shadow: -8px -8px 15px rgba(255,255,255,0.1);
  cursor: pointer;
}
.eql{
  font-size: xx-large;
  background-color: orange;
}
.op{
  color: rgb(4, 225, 4);
 
}