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.