demo.css

html,
body {
  font-family: 'Helvetica Neue', Arial, sans-serif;
}

body {
  padding: 20px 10vw;
}

h1 {
  font-size: 50px;
  margin-bottom: 100px;
}

h2 {
  font-size: 30px;
  margin: 30px 0 15px;
}

h4 {
  font-size: 18px;
  margin: 0 0 10px;
}

a {
  color: #000;
}

#obj {
  width: 100px;
  height: 100px;
  background-color: #000;
  margin-bottom: 100px;
}

.demo-playground form {
  position: relative;
  z-index: 10;
  display: flex;
}

.demo-playground form > * + * {
  margin-left: 30px;
}

#grad {
  width: 100%;
  height: 200px;
  margin-right: 10px;
}

.demos {
  display: flex;
}

.demo {
  flex: 1;
}

.cols {
  display: flex;
}

@media screen and (max-width: 800px) {
  .demos {
    display: block;
  }

  h1 {
    margin-bottom: 50px;
  }

  .demo-playground form {
    display: block;
  }

  .demo-playground form > * + * {
    margin-left: 0;
    display: none;
  }
}