three.js/threejs/lessons/resources/index.css

body {
  margin: 0;
  width: 100vw;
}
.lesson-main>* {
    margin: 1em 0;
}
iframe.background {
    position: fixed;
    width: 100vw;
    height: 100vh;
    border: none;
    top: 0;
    z-index: -1000;
}
.container {
    margin: 2em auto;
    padding: 15px 50px;
    border-radius: 25px;
    background-color: rgba(255, 255, 255, 0.9);
    max-width: 700px;
    width: 80%;
}
#language {
    margin-top: -2em;
    width: auto;
    font-size: large;
}
.rss {
   float:right;
   width:46px;
   height:46px;
}
.rss img {
   width: 46px;
   height: 46px;
}


@media (max-width: 600px) {
    .container {
        padding: 15px 20px;
    }
}