style.css

@import url('https://fonts.googleapis.com/css2?family=Ubuntu:wght@300;400;500;700&display=swap');

*{
    margin: 0;
    padding: 0;
    font-family: 'Ubuntu';
}

body{
    background: #43a047;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
}

.container{
    width: 360px;
    height: 400px;
    margin: 8% auto;
    background: #fff;
    border-radius: 8px;
    position: relative;
    overflow: hidden;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1); 
}

h3{
    text-align: center;
    margin-bottom: 40px;
    color: #777;
}

.container form{
    width: 280px;
    position: absolute;
    top: 100px;
    left: 40px;
    transition: 0.5s;
}

form input{
    width: 100%;
    padding: 10px 5px;
    margin: 5px 0;
    border: 0;
    border-bottom: 1px solid #999;
    outline: none;
    background: transparent;
}

::placeholder{
    color: #777;
}

.btn-box{
    width: 100%;
    margin: 30px auto;
    text-align: center;
}

form button{
    width: 110px;
    height: 35px;
    margin: 0 10px;
    background: linear-gradient(to right, #1565c0, #1976d2);
    border-radius: 30px;
    border: 0;
    outline: none;
    color: #fff;
    cursor: pointer;
    font-weight: 700;
    font-size: 0.8em;
}

#form2{
    left: 450px;
}

#form3{
    left: 450px;
}

.step-row{
    width: 360px;
    height: 40px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    box-shadow: 0 -1px 5px -1px #000;
    position: relative;
}

.step-col{
    width: 120px;
    text-align: center;
    color: #333;
    position: relative;
}

#progress{
    position: absolute;
    height: 100%;
    width: 120px;
    background: linear-gradient(to right, #1565c0, #1976d2);
}

small{
    color: #fff;
    font-weight: 700;
    font-size: 0.8em;
}

#progress::after{
    content: '';
    height: 0;
    width: 0;
    border-top: 20px solid transparent;
    border-bottom: 20px solid transparent;
    position: absolute;
    right: -20px;
    top: 0;
    border-left: 20px solid #1976d2;
}