Great, even for just a demo!
I'm really impressed with the combination of some brighter colors and feels to give it a cartoon-y feeling, but the presentation of it all still kept that mysterious ambiance, which is something I'm assuming you're going to wanna keep. All of it looked really consistent and just plain beautiful; great job on that. The intro kind of reminded me of a comic-book style of art, which I thought looked really nice and think you should keep that sort of thing for cut-scenes.
I feel kind of disappointed with the story though. I didn't really get a chance to learn anything about the characters, or anything at all really. Then again this is a demo and as said in your description, you're releasing it to get some feedback while graphics and such are in development, so it's a bit understandable, but I think you should have held out a little longer and lengthened it a bit more. Some of the story I did see though had a few typos and such, so you might want to fix those and revise the scripts.
Controls are probably where I tear off a point. I found they were a bit awkward, with so many buttons in odd positions that it was difficult to grasp, even near the end of the demo. I think instead of using "A" to jump, you should just change it to the up arrow key. Another thing I think you could change is the pressure release button; why have a completely separate button for something that seems like it'll only ever get one use? I think instead of a separate button, maybe make the player just double-tap (or even repeatedly tap) the firing button again, that way you can just assign the rest of the buttons to "A," "S," "D," and "F," which I think would be pretty manageable.
The general gameplay was very nice; I didn't feel rushed, which was good because I liked just looking around the place and staring at some of the beautiful art. One thing I didn't like though is when I was walking into a room on the right and because of the instantaneous transition, I fell right into acid. You might want to make the platform before that drop a little longer, otherwise I think many others could fall victim to this as well. I also found that the kick button didn't seem to have any use in this demo, which I only noticed when I finished the demo and went back to the controls.
Sound isn't really a part of a game that I am very good with (or at least music specifically) but the few sounds that were in the game sounded great. Very crisp and they all fit really well. The music throughout the game was pleasantly calm and didn't over or under-power the mood of the game. But when I fought my first monster, the music kind of got a kick and started going, which I'm not complaining about, I just felt that it further helped set the mood of the game.
I hope my review has helped give you some of that feedback you wanted for your game. You guys have a great game going on right now, and I'm eagerly awaiting an update or even the full game.
