Pretty neat game! I like the mechanic of mixing and matching various gun attachments: not only is it fun to build up your own personal god gun, it leads to playthroughs feeling different from one another thanks to the risk/reward of certain attachments and how they make you improvise or compensate for them. The game overall feels very smooth and impactful as well: good use of bullet feedback and screenshake and other subtle techniques, and I like the way you can see immediate feedback for effects like crits. I also always like me a good boss, and I was glad to see this game deliver a lot of neat bosses every 10 levels.
In terms of complaints, the game, while fun and volatile thanks to the gun customization, can still be a little generic and easy at times in regards to the basic shooting mechanics, simple enemy design, recycled levels and repetitive music and combat scenarios, leading to an overall staleness (except for bosses). Shooting felt a bit funny at times when you or enemies are close to walls, like in a narrow corridor: felt like bullets would just disappear without reason due to weird collisions or overlaps. Aiming could get a little wonky as well due to the offset of your body and shoulder switching in those certain degrees. I also wish the game would lock the cursor as trying to fire near the edge of the screens can lead to you clicking out and losing control. While it's a minor thing, I also would like a crosshair on screen in game. Still, very nice work on this one!