Hey I recognize those ammo sprites!
I'm not much into the idea of a time trial target thing as opposed to, for example, a sidescroller with actual enemies.
It feels like it'd get repetitive fast especially if there's no time limit and you can clear levels by taking your time.
Great job with the juice, the weapons and sound effects are punchy.
The arsenal seems good enough for what you're trying to do, the shotgun doesn't seem to really have a place I'd make it have some knockback so it doubles as a mobility tool, TF2 force-a-nature style. It's a fun trope I even added that in my game.
The only thing I don't like about the movement is that you can't fire up or down when sliding on a wall: it's easy to accidentally snap to it when trying to hit a target that's above you.
It also might be nice if holding down while mid-air gave you downward velocity, it could be used to get on downward slopes faster or just better air control depending on how tricky you intend to make the level.
Cool start though, I'll check this out again next time.