It's fun, and looks, sounds, and feels good to play. There's a lot of room for expansion which is a great thing if you want to continue to develop the game.
The alternate weapons (shotgun, smg) feel a bit weak though mostly due to energy usage. I can see the shotgun being a good emergency weapon though.
My favorite mechanic was using the enemies' bullets against large groups to explode and clear a room more quickly and safely. I think it'd be great when expanding on enemies to continue to add ways to use their strengths against them.
Great job to everyone involved; it's a very clean game and a good experience to play!