Eversion

When I started Eversion I thought that it’s a cheap Mario clone. Then, when I could change the world like in Giana Sisters: Twisted Dreams, I still thought that it’s a cheap clone with a gimmick; but when I could change the world again and I kept seeing the differences between all the worlds, I finally understood this game’s charm. Eversion has two endings, the first one, the “bad” one, is relatively easy to find. The levels are pretty short and I only got really stuck once. You might really have to work for the “good ending”, especially if you want to find it on your own (without walkthroughs or guides).