A simple engine for rendering a progress bar using pen blocks. Note that this uses the "clear" block, so it won't work with pen projects. This engine also supports the creation and use of skins, which you can create by copying dark_bar and dark_draw, renaming them to *_bar and *_draw, where * is whatever you want to call the skin, and then editing it from there. Then you can use the skin by putting the skin name in the block.
