http://insideastarfilledsky.net/It's a game about procedurally generated creatures in a procedurally generated world that is another creature which is in...
The gameplay is that of a top down shooter, using the mouse to aim, shooting enemy creatures and grabbing powerups. The trick is that powerups don't apply to you but to the thing you're inside of. By default you're inside the next higher player creature but you can also enter powerups and enemies (kinda like Disgaea's item world) to affect their properties by grabbing powerups in there. Don't like that lv1 corner shot that's blocking your path? Dive in and turn it into a lv15 health boost or something by replacing its powerups with health powerups! Can't find health powerups inside the powerup? Dive into a different powerup in there and replace its powerups with health powerups! It's powerups all the way down! And hey, if that enemy is so annoying just go in and replace its range attack and dodging AI with sticky shots!
Shot powerups combine, kinda like the stages in the Blast Works editor. Stick a burst and a spread powerup on your creature and you shoot a spreadshot that explodes into even more spreadshots! Of course if you invest all three powerup slots into shot powerups that means one hit will send you packing so maybe you'd want a health powerup instead.
If you get killed you get dropped into your current player creature so fix it up, stick some better powerups on there and go back into the fight!