HTML

CSS

JS

* {
    margin: 0;
    padding: 0;
    font: inherit;
}

body {
    font-family: "Roboto", sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #FDF4F5;
}

h2 {
    font-size:2rem;
}

.login-form {
    position: relative;
    width: 380px;
    height: 420px;
    background: #AEDEFC;
    border-radius: 8px;
    overflow: hidden;
}

.login-form::before {
    width: 380px;
    height: 420px;
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    transform-origin: bottom right;
    background: linear-gradient(0deg, transparent, transparent, #192655, #192655, #192655);
    z-index: 1;
    animation: animate 6s linear infinite;
}

.login-form::after {
    width: 380px;
    height: 420px;
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    transform-origin: bottom right;
    background: linear-gradient(0deg, transparent, transparent, #192655, #192655, #192655);
    z-index: 1;
    animation: animate 6s linear infinite;
    animation-delay: -3s;
}

.border-line {
    position: absolute;
    top: 0;
    inset: 0;
}

.border-line::before {
    width: 380px;
    height: 420px;
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    transform-origin: bottom right;
    background: linear-gradient(0deg, transparent, transparent, #005B41, #005B41, #005B41);
    z-index: 1;
    animation: animate 6s linear infinite;
    animation-delay: -1.5s;
}

.border-line::after {
    width: 380px;
    height: 420px;
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    transform-origin: bottom right;
    background: linear-gradient(0deg, transparent, transparent, #512B81, #512B81, #512B81);
    z-index: 1;
    animation: animate 6s linear infinite;
    animation-delay: -4.5s;
}

@keyframes animate {
    0% {
        transform: rotate(0deg);
    }

100% {
        transform: rotate(360deg);
    }
}

.login-form form {
    background: #DAF5FF;
    position: absolute;
    inset: 4px;
    padding: 50px 40px;
    border-radius: 8px;
    z-index: 2;
    display: flex;
    flex-direction: column;
}

.login-form form h2 {
    color: #192655;
    font-weight: 700;
    text-align: center;
    letter-spacing: 0.1rem;
}

.login-form form .input-box {
    position: relative;
    width: 300px;
    margin-top: 35px;
}

.login-form form .input-box input {
    position: relative;
    width: 100%;
    padding: 20px 10px 10px;
    color: #AEDEFC;
    background: transparent;
    border: none;
    outline: none;
    box-shadow: none;
    font-size: 1rem;
    font-weight: 700;
    letter-spacing: 0.05rem;
    transition: 0.5s;
    z-index: 10;
}

.login-form form .input-box span {
    position: absolute;
    left: 0;
    padding: 20px 0px 10px;
    pointer-events: none;
    color: #7286D3;
    font-size: 1rem;
    letter-spacing: 0.05rem;
    transition: 0.5s;
}

.login-form form .input-box input:valid~span,
.login-form form .input-box input:focus~span {
    color: #192655;
    font-size: 0.75rem;
    transform: translateY(-34px);
}

.login-form form .input-box i {
    position: absolute;
    left: 0;
    bottom: 0;
    width: 100%;
    height: 2px;
    background: #192655;
    border-radius: 4px;
    overflow: hidden;
    transition: 0.5s;
    pointer-events: none;
}

.login-form form .input-box input:valid ~ i,
.login-form form .input-box input:focus ~ i {
    height: 44px;
}

.login-form form .links {
    width: 300px;
    display: flex;
    justify-content: space-between;
}

.login-form form .links a {
    margin: 10px 0;
    font-size: 0.75rem;
    color: #7286D3;
    text-decoration: none;
}

.login-form form .links a:hover,
.login-form form .links a:nth-child(2) {
    color: #192655;
}

.login-form form input[type="submit"] {
    border: none;
    outline: none;
    padding: 9px 25px;
    color: #AEDEFC;
    background: #192655;
    cursor: pointer;
    font-size: 0.9rem;
    border-radius: 4px;
    width: 100px;
    margin-top: 10px;
    font-weight: 600;
}

.login-form form input[type="submit"]:hover,
.login-form form input[type="submit"]:active {
    opacity: 0.8;
}

@media (max-width: 400px) {
    .login-form form {
        padding: 50px 30px;
    }
}

Animated Login Form with Validations

Very elegant and modern login form. This form has two main features:

Animated gradient border circling the form
Simple data validations for Username and Password without using JavaScript