The aiming is fucked, the gun should always point at where the cursor is.
The isometric controls are bizarre in a game like this, I think it would be better if they were relative to the camera instead of the level.
Lighting is too dark and uniform and it's hard to see weapons on the ground, who forgot to pay the bills? The field of view is too small and it's easy to get killed by someone offscreen, maybe make the camera follow the player's cursor a bit.
The gunplay is pretty satisfying once you get used to the weird controls, clearing a room with the FN FAL was fun, it certainly has that Hotline Miami feel to it. Running out of ammo in the middle of a gunfight and being chased by bad guys while you scramble to find another gun is exciting and I could play this for a long while when it gets more polished.