I find it hard to believe you're a first time programmer/artist/etc, because this is very good! The game is satisfying to play and not hard to figure out. The sound effects are nice, they don't feel overwhelming.
I would recommend you have a tutorial in the game rather than having a page that explains everything. Interactive instructions are always more enjoyable!
The one thing I didn't like here was the need to find every red block in order to advance. In a couple of the levels it felt tedious to go back through the whole level to figure out what I missed. At the very least, a sign by the portal saying "There a X red blocks left" would have been good.