style.css

body{
    background: #222;
    font-family: 'Poppins', sans-serif;
}

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.video-section{
    background: url(img/bg.jpg);
    background-size: cover;
    height: 60em;
    display: flex;
    justify-content: center;
    align-items: center;
}

.yt-modal-btn{
    background: #ff3232;
    border: none;
    display: block;
    width: 4em;
    height: 4em;
    border-radius: 50%;
    font-size: 1.5em;
    color: #fff;
    transition: 0.3s;
    cursor: pointer;
}

.yt-modal-btn:hover{
    background-color: #fff;
    color: #ff3232;
}

.modal-bg{
    position: fixed;
    top: 0;
    left: 0;
    background: rgba(0, 0, 0, 0.8);
    width: 100vw;
    height: 100vh;
    backdrop-filter: blur(5px);
    overflow-y: scroll;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    transition: opacity 0.4s ease-in-out;
}

.modal{
    width: 90vw;
    position: relative;
    padding-top: 56.25%;
    margin: 2em 0;
}

.modal iframe{
    position: absolute;
    top: 0;
    left: 0;
    border: none;
    width: 100%;
    height: 100%;
}

/* Hide the modal */
.modal-bg{
    display: none;
    opacity: 0;
}

h1{
    font-size: 5em;
}

.placeholder-content{
    text-align: center;
    color: #fff;
    padding: 2.5em;
}

.placeholder-content p{
    text-align: center;
    line-height: 27px;
    font-size: 1.4em;
    margin: 1em 10em;
    letter-spacing: 0.05em;
}

/* You can set a limit to how much the video grows with the screen size */
@media screen and (min-width: 900px){
    .modal{
        padding-top: 0;
        width: 809px;
        height: 505px;
    }
}