test.css

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

body {
    height: 100vh;
    width: 100%;
    background-image: url(/img/bg.png);
    background-size: cover;
    background-position: center;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0 10%;
}

.container {
    width: 100%;
    max-width: 470px;
    padding: 30px 20px;
    background: rgba(10, 10, 10, .45);
    border: 2px solid #3a1b22;
    border-radius: 16px;
}

.container h1 {
    text-align: center;
    color: #fff;
    font-size: 2.5rem;
    font-weight: 600;
    padding: 0 0 8px 0;
}

.container form {
    padding: 0 50px;
}

form .main {
    position: relative;
    margin: 30px 0;
    border-bottom: 2px solid #3a1b22;
}

.main input {
    width: 100%;
    padding: 0 5px;
    font-size: 1rem;
    height: 40px;
    border: none;
    outline: none;
    background: none;
    color: #e7e6e6;
}

.main label {
    position: absolute;
    top: 50%;
    left: 6px;
    color: #b2405d;
    transform: translateY(-50%);
    font-size: 1.1rem;
    pointer-events: none;
    transition: all .40s ease;
}

.main span::before {
    position: absolute;
    content: '';
    left: 0;
    top: 35px;
    width: 100%;
    height: 2px;
}

.main input:focus~label,
.main input:valid~label {
    top: -3px;
    color: #fff;
}

.pass {
    margin: -6px 0 20px 5px;
    color: #fff;
    cursor: pointer;
}

.pass:hover {
    text-decoration: underline;
}

input[type="submit"] {
    height: 45px;
    width: 100%;
    border: none;
    background: #b2405d;
    color: #fff;
    font-size: 1.1rem;
    border-radius: 16px;
    cursor: pointer;
}

.signup {
    color: #b2405d;
    font-size: 1rem;
    text-align: center;
    margin: 30px 0;
    cursor: pointer;
}

.signup a {
    margin-left: 10px;
    text-decoration: none;
}

.signup a:hover {
    text-decoration: underline;
}

@media (max-width: 525px) {
    body {
        padding: 0 2%;
    }

    .container {
        padding: 10px 5px;
    }
}