Played the demo, excellent stuff. Some remarks:
The text is too tiny on real hardware, for people who needs (better) glasses. An optional bigger font for the dialogue text would be nice.
When jumping up shafts, the screen transitions too soon when we need to jump alternating between the left and right on those tiny platforms in the walls of the shaft. We try to jump onto a tiny platform on the left, and before reaching it the screen transitions and in the new screen the first platform is on the right, which is disorienting.
As for the rest of the game, it's really well made and I hope it gets fully funded. I find that the lack of vertical aiming is an interesting differentiation between this game and the Metroid series, because it opens new challenge possibilities in the level design. Maybe the diagonal or vertical aiming could be exclusive to certain weapons.
