Wow, good job with the game, and on Love2D no less! I really enjoyed the concept of losing your upgrades over time, and the fights were all very good. I had a lot of fun, but the crashed unexpectedly when I was about to defeat Number I. I'll post the error here:
Error
boss.lua:2930: bad argument #1 to 'draw' (Drawable expected, got nil)
Traceback
[C]: in function 'draw'
boss.lua:2930: in function 'draw'
main.lua:282: in function 'draw'
[C]: in function 'xpcall'