Hold your laughter.
What we have here is one of the most demonic, satanic, ominous abominations of a flash game ever created.
Only four people have reported clearing it. The last three stages are so notoriously difficult that only one or two people every few hours report making any progress on the threads on /v/ or reddit
You can upgrade on the stage select screen.
Stage 6, 7, and the extra stage are where the real difficulty is at. I haven't cleared stage 7 yet.