Great work on the demo! Its plays quite nicely and the visuals are really good too.
I'm sure this will be updated in future releases but I'm currently able to fall off the map in the place that has no wall (looks like a doorway).
I sometimes find it hard to know which enemies I'm shooting at when there's a hoard of enemies. I think part of this is because the flash effect is the same color as the shooting reticule ball.
When you get too close to objects they become transparent which is nice since it allows you to see what's happening in the game better. However, I was wondering if this should be combined with camera zoom/clamp so that it prevents the player from seeing outside of the map (like on the outer walls of the map, if you're too close then you can see out of the map).