Videos only do so much, so I wanted to let you guys know what I thought of the game after spending about half an hour playing it.
Visuals: Absolutely brilliant. The backgrounds are just fantastic, you've done a great job of making me feel like I'm in a 2-D world that still has depth. I don't notice any repetition in the environments, either, I feel like I'm really exploring a physical location. Naija's sprite is absolutely adorable! Fits very well with the rest of the game. Energy effects look great too. My only tiny complaint is with the minimap in the bottom right corner. It's a little fuzzy, and sometimes it can be hard to read. But hey, double click, and you get a crystal clear map. So not a big deal.
Controls: Bravo. Naija swims so fluidly to the movements of my mouse. And the controls you picked are extremely intuitive. The singing interface is great, as well. The energy blasts are fantastic. Also, controlling Naija is a breeze, and you really notice it in combat situations. I love being able to dart between enemies and pummel them with energy blasts. Bravo!
Sound: The only track I was lukewarm on was the Energy Temple track, but I still think it worked well. The other songs I've encountered so far are brilliant, they really complement the atmosphere set by the visuals. Jenna's voice acting is top notch. Even the expressions of pain and surprise. Often, those are the only voice bits that irritate me in otherwise flawless voice acting, but here they sound great.
Gameplay: The only non-positive comment I can make here is that I can see someone wary of this game playing for 15 minutes and throwing it down, claiming that nothing happens. The first 15 minutes of simple exploring could be a turnoff to some, but I enjoyed seeing all the new sea life and examining the backgrounds. After your first big power upgrade, though, the pace really picks up.
Story: This obviously is the least developed point, but I'll speak to it, anyway. I am left wondering about a lot, but I have enough to go on so that I have some structure to my wondering. I think you balanced knowing and not knowing wonderfully.
So that's it for now. As I come across new things to say, I'll post them. Fantastic job, guys! Well worth my purchase!