style.css

body {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

#logIn,
.inputContainer {
    padding: 40px;
    margin: 20px;
    border-radius: 5px;
    box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);
}

#logIn h2 {
    text-align: center;
}

#mainContent {
    display: none;
    min-width: 70%;
}

#mainContent .content {
    color: #fff;
    padding: 30px 50px;
    border-radius: 7px;
}

#mainContent .content h2 {
    margin: 0;
    font-size: 3rem;
}

#mainContent  .col-md-4:first-child .content {
    background-color: #f1c40f;
}

#mainContent  .col-md-4:nth-child(2) .content {
    padding: 30px 50px;
    background-color: #2ecc71;
}

#mainContent  .col-md-4:last-child .content {
    background-color: #e74c3c;
}

.inputContainer {
    margin: 0px 25px;
}