This demo is quite promising. The gameplay was pretty intense and there is always something happening, which I appreciate.
My main critique would be that it feels like it could be more immersive. I think what I mean by that is that the game seems kind of flat even though there is a lot of action. But this is just a demo, so hopefully some volumetric lighting, ambient occlusion, and particle effects can be added to the game eventually, which would go a long way toward giving it the immersion I feel it is lacking. Overall I think it was fun and is a good starting place to make a really great game.