Wonderful game to play, and its difficulty was definitely manageable. Unlike some other logic-based games on Newgrounds, this wasn't too hard for me to complete. I like how you used the concept of infinite lives, and put it to use in your levels. I also like the bit-style art choice, as well as the premise of the story. I also think that the epilogue was well-executed.
However, I do think the final boss level was too easy, especially when compared to the key levels. It actually took me more attempts to do some of the normal levels (especially the later ones) than the attempts I took to defeat the final boss. Also, when there were more sprites on-screen, my game noticeably lagged quite a lot. Not sure if it's my computer or not.