main.css

html, head, body {
  background: #111;
  color: #fff;
  margin: 0;
  font-family: Roboto;
}

body {
  display: flex;
  flex-direction: row;
}
#preview {
  flex: 2;
  position: relative;
}
#tools {
  flex: 1;
  display: flex;
  align-items: center;
}

#tools > div {
  width: 100%;
  max-width: 400px;
}

#preview > canvas.tex {
  display: none;
  opacity: .5;
}
#preview > canvas {
  border-radius: 3px;
  position: absolute;
  top: 50%;
  left: 95%;
  transform: translateX(-100%) translateY(-50%);
}
#preview.text > canvas.tex {
  background: #000;
  border: 1px solid rgba(255, 255, 255, .2);
  box-shadow: 0 2px 8px rgba(255, 255, 255, .05);
  display: block;
}
#preview.notext > canvas.gl {
  background: #000;
  border: 1px solid rgba(255, 255, 255, .2);
  box-shadow: 0 2px 8px rgba(255, 255, 255, .05);
}

@media (max-width: 800px) {
  body {
    flex-direction: column;
  }
  #preview {
    flex: min(100vw, 600px) 0;
  }
  #preview > canvas {
    top: 95%;
    left: 50%;
    transform: translateX(-50%) translateY(-100%);
  }
  #tools {
    align-items: start;
  }
  #tools > div {
    margin: 0 auto;
  }
}

.close-button {
  display: none
}