I really enjoyed this one! I just dig how simple it is, and there is something about it that does really speak to the feel of old flash games. It feels like something I would've played on a school computer in middle school or something, and I mean that in the best way! It just has a nice vibe.
I didn't love some of the level design. Occasionally it would feel a bit like there were just enemies all over the place, and the setup of little gap with an enemy going back and forth in it started to feel a bit overused in my opinion. But that could also just be because I was pretty terrible at the game too, haha. I did really like the concept of the level where you had walls of enemies on either side of you; that mixed things up a bit!
Overall, awesome work! I got nine coins... wanted to go back and get the final one so I could play the extra level, but it seemed like it meant playing the whole thing again, and I oughta rate some other games today. Maybe I'll come back at some point!