The current catchbook is simple yet powerful. I have started to make most of my technical sketches on Catchbook. But when I color/shade my sketches, the color overflows and hides the sketched boundaries (if alpha is 100%) as I apply color/shade after making the outlines. I wish I could just "push" the color to a layer below the outline sketch layer. Other times, I wish I could draw certain items on different layers so that I could selectively make the layers visible/invisible depending on need. So, I really hope to see a simple "layers" feature in Catchbook in future.