index.css

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    list-style: none;
}

section {
    position: relative;
    width: 100%;
    height: 100vh;
    display: flex; 
}

section .imgBx {
    position: relative;
    width: 50%;
    height: 100%;
}

section .imgBx img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
}

section .contentBx {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 50%;
    height: 100%;
}

section .contentBx .formBx {
    width: 50%;
}

section .contentBx .formBx h2 {
    color: grey;
    font-weight: 600;
    font-size: 1.5em;
    text-transform: uppercase;
    margin-bottom: 20px;
    border-bottom: 4px solid #000;
    display: inline-block;
    letter-spacing: 1px;
}

section .contentBx .formBx .inputBx {
    margin-bottom: 20px;
}

section .contentBx .formBx .inputBx span {
    font-size: 16px;
    margin-bottom: 5px;
    display: inline-block;
    color: #607d8b;
    font-weight: 300;
    letter-spacing: 1px;
}

section .contentBx .formBx .inputBx input {
    width: 100%;
    padding: 10px 20px;
    outline: none;
    font-weight: 400;
    border: 1px solid #607d8b;
    font-size: 16px;
    letter-spacing: 1px;
    color: #607d8b;
    background: transparent;
    border-radius: 30px;
}

section .contentBx .formBx .inputBx input[type="submit"] {
    background: #607d8b;
    color: #fff;
    outline: none;
    border: none;
    font-weight: 600;
    cursor: pointer;
}

.remember {
    margin-bottom: 10px;
    color: #607d8b;
    font-weight: 500;
    font-size: 14px;
}

section .contentBx .formBx .inputBx p {
    color: #607d8b;
}

section .contentBx .formBx .inputBx p a {
    color: #607d8b;
}

section .contentBx .formBx h3 {
    color: #607d8b;
    text-align: center;
    margin: 80px 0 10px;
    font-weight: 500;
}

section .contentBx .formBx .sci {
    display: flex;
    justify-content: center;
    align-items: center;
}

section .contentBx .formBx .sci li img {
    list-style: none;
    width: 50px;
    height: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #000;
    border-radius: 50%;
    margin: 0 7px;
    cursor: pointer;
}

@media (max-width: 768px) {
    section .imgBx {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
    }

    section .contentBx {
        display: flex;
        justify-content: center;
        align-items: center;
        width: 100%;
        height: 100%;
        z-index: 1;
    }

    section .contentBx .formBx {
        width: 100%;
        padding: 40px;
        background: #fff;
        margin: 50px;
    }

    section .contentBx .formBx h3 {
        color: #607d8b;
        text-align: center;
        margin: 30px 0 10px;
        font-weight: 500;
    }
}