<div class="form">
    <h1>welcome</h1>
    <form class='user-form' return false>
        <input type="text" placeholder=' name'>
        <input type="text" placeholder='email'>
        <input type="text" placeholder='username'>
        <button>submit</button>
    </form>
</div>

body {
    height: 100vh;
    margin: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: url("https://images.unsplash.com/photo-1498252207774-50583342eb33?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=fbb3eaf679cff8fcdeb91c2e20b5d5a5&auto=format&fit=crop&w=2250&q=80");
    background-size: cover;
    background-repeat: no-repeat;
    font-family: "Quicksand", sans-serif;
}
.form {
    background: #ffffffa3;
    height: 400px;
    width: 400px;
    border-radius: 5px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
}
.user-form {
    width: 300px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
}

.user-form input,
.user-form button {
    height: 50px;
    margin: 10px 0;
    background: #ffffffa3;
    border: none;
    font-size: 23px;
    text-align: center;
        font-family: "Quicksand", sans-serif;
    transition: all .7s;
}

.user-form input {
    border-bottom: 2px solid #000;
}

.user-form button:focus {
    background: #fff;
}

.user-form input:focus {
    background: #fff;
}