Ah man. Thank you so much for trying out the game and especially for taking the time to write such an extensive comment. I really appreciate the folks that get engaged enough to take their own time to do this and you went all out with an extensive view. There's really not much I can reply back other than apologize for the game performance drops. I really did not have time to care about optimizations during the week that I took to make this but I'll certainly try to look into making the game perform better in future versions. As for the theme, again, it's my bad for not making it clear. I wanted to make an action based game so... To run with the theme I made the hearts actually point out the difficult points on each level. I realize that it is not obvious but without the hearts the player would have much less information about what's going on. So when each heart is taken, the player is left with nothing but his memory to guide him. That, and of course, bullets. This encourages the player to think just a little before collecting the hearts in the sense that they actually make the player blind. Then I added the hearts chasing the player mechanics to mess it all up. This is to say that the theme is there... It's just not obvious.
Finally... the spikes... Ah... those spikes... I get your point and I had doubts about those myself. But the fact is that on that gauntlet I needed to stop the player at that point. Even if only for 0.2 seconds, the player needs to think for a split second and make a slightly less horizontal jump to overcome the obstacle. If not spikes, I would use enemies or something like that. Of course, not everyone is ok with that and I think that is your case. I hope that it didn't mess up your experience too badly though.
All in all, I truly appreciate those kind of comments. They help me make better and more satisfying games.