I really liked this game. I know I suck at platformers in general, so most of my issues were dealt with by simply gitting gud, else I wouldn't get any far into the game.
The characters are simple but charming, the graphics/art were neatly put together, the music didn't get annoying, and finally, the fast respawning and no life mechanics were great.
That said, I'm not sure how well optimized the game has been, for the 'second' level (the one with the red, blue and white squares with phasing rotation platforms) suddenly got REALLY slow and the framerate dropped a bunch, and I found myself getting easily stuck between the phasing platforms by the time more white became prominent and I just found out they were 'shootable'.
Couldn't Missileman really just... shoot up? I'd easily not bother with these found glitches if he could just do that. Pretty sure you're referencing Mega Man, but keep those in mind.