We added the health system at the very end because it was pretty hard to go through the whole thing haha! I'm not fond of checkpoints because it's a rather short game (4 minutes), and I think that going through it every time only helps you to understand and memorise the patterns (especially the lasers). But I understand that it can be frustrating ^^' As for the dash, we were afraid that it would make the game to forgiving and easy. JSaB and Undertale's boss fights are our main inspirations, indeed ^^
Thanks a lot for this comment!