I'm going to preface this by saying I'm neither gay nor a furry, and that I played this title solely for the gameplay. Being real, though, the MC is more monster boy than furry. Not that it matters, just an observation.
The game is a DOOM clone that only consists of three levels, but I found myself having fun regardless of how short it is. Mousegun's unique mechanic is a melee attack that provides health drops upon successfully slashing enemies, which creates a nice risk-rewards system for the player. Similar to the modern DOOM games incentivizing players to chainsaw weak enemies for ammo, I found myself treating basic mukes like walking health packs that could be cut open whenever needed. While the overcharge mechanic on health is a novel idea, though, I don't think it jives as well as armor does. Yes, it creates more risk-reward depending on when you need the extra boost to push through an area, but I rarely found it actually useful when compared to basic healing since overcharge dissipates over time.
Guns see the standard pistol, submachine gun, and shotgun in the fray. They work as they should, no good or bad deviations from the formula. I do find it strange that you get the submachine gun before the shotgun, but it's not like they're far apart to begin with. Being able to keep weapons between stages makes going back for 100% and speed run times less annoying. Starting with the ammo you had at the end of the last level instead of a fresh cache isn't desired, but DOOM did it so I can't complain too much.
Enemy variety is alright for a game this size. You've got basic grunts that slash you, fat guys with slow firing guns, beefies that take more firepower to kill, and stationary turrets that shoot quickly. The game noticeably lags in rooms full of those bullet-spraying turrets, which can make taking them out a pain. Otherwise, this is a relatively easy game if use cover optimally and slash enemies to restore health when needed. The final boss is a thing that exists, but it's incredibly easy and isn't a memorable fight in the slightest.
H-content is nearly non-existent, with a pin-up for beating all levels 100% and a short animation for clearing them in under 15 minutes collectively. Not an issue for me, though I imagine it's a bit disappointing for someone into this. That said, all the game's art is super smooth and appealing to the eye, which merits you at least give it a quick look.
For the size this project is, Mousegun isn't half bad. It's not anything earthshattering, but it's a fun way to burn an hour if you've got it. It'd be cool to see this get expanded into a bigger game, perhaps introduce some new weapons and enemies into the fray. I suppose only time will tell.