It's a pretty straight forward shooter, everything works from beginning to the end, not bad.
Using all 2D sprites to recreate the original DOOM like art-style is pretty resourceful
Now from the art style and enemy types, I assume it's using the original DOOM as a reference.
In that sense, I feel like not all mechanics are well suited for that type of gameplay.
Slowing down when aiming may not be suitable for the that sub-genre of arcade shooter. At medium/close range It is near impossible to dodge during aiming. It makes movement during aim feels like a useless mechanic.
However if the player stays far away from the enemy, the slow movement during aim can completely dodge all bullets. This may have made distance too much of a factor in affecting difficulty.
In the last boss fight, simply circling around at the edge of the room, holding aim all the way, still dodges nearly all of the boss's blue fire and minion shotgun blasts.
Nonetheless, good job on making a complete game in time, that's better than I did, so that's a job well done to me.