style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Poppins", sans-serif;
}
body{
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: black;
}
#title{
    background-color:transparent;
    color: rgb(255, 255, 255);
    border-radius: 40px;
    box-shadow: rgba(0, 0, 0, 0.16) 0px 1px 4px, rgb(51, 51, 51) 0px 0px 0px 3px;

}
#description{
    background-color: transparent;
    color: white;
    border-radius: 20px;
    box-shadow: 0px 9px 30px rgba(249, 248, 246, 0.3);

}
.container{
    margin: 0 auto;
    position: relative;
    max-width: 300px;
    width: 100%;
    border-radius: 12px;
    padding: 10px 20px 20px;
    background: #dadada;
}
.display{
    background-color: #b9b9b9;
    height: 80px;
    width: 100%;
    margin-bottom: 10px;
    font-size: 25px;
    text-align: right;
    outline: none;
    border: none;
    pointer-events: none;
}
.buttons{
    display: grid;
    grid-gap: 10px;
    grid-template-columns: repeat(4,1fr);
}
.buttons button{
    padding: 12px 10px;
    border-radius: 6px;
    border:none;
    background-color:#dadada;
    font-size: 20px;
    cursor: pointer;
}
.buttons button:active{
    transform: scale(0.99);
}
.operator{
    color: blue;
}
#title,#description{
    color: white;
    text-align: center;
    margin: 20px 0;
    padding: 10px 15px;
}