styles.css

/*// ©Copyright Mr.SGC //
***Proudly made in INDIA*** 
*/

body{
    margin: 0;
    padding: 0;
    text-align: center;
    font-family: sans-serif;
    background-image: linear-gradient(120deg,#ff6600, #fff, #0e9901);
    min-height: 100vh;
}
div{
    width: 500px;
    position: absolute;
    top: 50%;
    left: 50%;
    background: linear-gradient(to right, #ff6600, #fff, #0e9901);
    transform: translate(-50%, -50%);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 1px 1px 20px #0004ff;
}
h2{
    font-size: 30px;
    font-weight: 600;
}
.text{
    text-align: left;
    margin-left: 150px;
}
#w, #h{
    color: #222f3e;
    text-align: left;
    font-size: 20px;
    font-weight: 200;
    outline: none;
    border: none;
    background: none;
    border-bottom: 1px solid #341f97;
    width: 200px;
}
    #w:focus, #h:focus{
        border-bottom: 2px solid #341f97;
        width: 300px;
        transition: 0.5s;
    }
    #result{
        color: #2f00ff;
    }
    #btn{
        font-family: inherit;
        margin-top: 10px;
        border: none;
        color: rgb(0, 0, 0);
        background-image: linear-gradient(120deg,#ff6600, #fff, #0e9901);
        width: 150px;
        padding: 10px;
        border-radius: 30px;
        outline: none;
        cursor: pointer;
    }
    #btn:hover{
        box-shadow: 1px 1px 10px #2f00ff;
    }
    #info{
        font-size: 12px;
        font-family: inherit;
    }