Its actually not that bad, one of my gripes would be the weird button placement. It just does not feel right to me. Second, and I get this is still in "testing" but some music and signs to progress into other areas of the map would have been great too.

Over all, not that bad actually.

Simple design, decent movement quality. Difficult firing pattern (one shot per jump?) also, was able to kill creatures before the screen revealed them (bullets connected with monsters I never saw but heard dying offscreen). Also, found myself in a dead end with no way forward but to backtrack and be killed. Boo

The graphics remind me of flash games from 2004-2008 which is a nice welcome but what isn't a nice welcome are the controls. The movement feels sluggish at best, and having J as the fire button makes my hands feel really cramped when jumping and shooting. I feel like L would have been a better choice for this type of control setup. The green coins as far as I'm concerned don't serve a purpose whatsoever. Maybe collecting 20 of them can earn you a free hit point?
Overall I think this should use a bit more work before it can be passable by today's standards.