Despite the bugs and unimplemented features, it used to be possible to play to the end of almost every level. However, as the code has evolved, some levels became impassable.
There's a new version up now, with several bug fixes. It's now possible to finish every single level. Trust me - I've spent much of the last few days doing exactly that!
P.S. There are now two Windows downloads. One contains all the files and libraries, the other one contains just an update.