style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&display=swap');
*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    width: 100%;
    height:100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: linear-gradient(45deg,#0a0a0a,#3a4452);
}
.calculator{
    border:1px solid #717377;
    padding :20px;
    border-radius: 16px;
   background-color: 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 rgb(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:50%;
    background: transparent;
    color:#ffffff;
    font-size: 20px;
    box-shadow: -8px -8px 15px rgba(255, 255,255, 0.1);
  cursor: pointer;
}
.equal{
    background-color: blue;
}
.operator{
    color:#ffffff;
}