. {
  overflow-x: hidden;
}

html {
  width: 100%;
  height: 100%;
}

body {
  width: 60vw;
  font-size: 1.1em;
  font-family: sans-serif;
  margin-left: auto;
  margin-right: auto;
}

p {
  display: block;
  width: 100%;
}

img {
  display: block;
  width: 70%;
  margin-left: auto;
  margin-right: auto;
}

.img-freecad-tut {
  width: 50%;
  display: block;
  margin-bottom: 30px;
  margin-left: 0;
  margin-right: 0;
}

iframe {
  width: 512px;
  height: 512px;
  overflow-x: hidden;
  overflow-y: hidden;
}

h1, h2 {
  text-transform: uppercase;
  color: #333;
}

h3, h4 {
  margin-top: 50px;
  margin-bottom: -10px;
  text-transform: uppercase;
  color: #333;
}

ul {
  margin-top: -10px;
  margin-bottom: 80px;
  list-style-type: none;
  padding: 0;
}

ul li {
  margin: 10px 0;
}

hr {
  margin-top: 40px;
  margin-bottom: 40px;
  border: 1px dashed grey;
}

@media only screen and  (max-width: 1600px) {
  .img-freecad-tut {
    width: 75%;
  }
}

@media only screen and (max-width: 600px) {

  html { }

  body {width: 90%;  font-size: 1.0em;}

  img {width: 90%;}

  h1, h2 {font-size: 1.2em;}

  h3, h4 {font-size: 1.1em;}

  .img-freecad-tut {
    width: 90%;
  }

}