So, it took God knows how many tries but I finally beat the last world of the regular game (light world, world 6).  I usually don't get animated when I beat a game but I literally threw my arm up in the air, sort of like Tiger Woods, and almost shouted in exultation.  So, how many here have finish the light world?  Has anyone finished the dark world? 

I've finished light and dark world.  Now I just need to go back and 100% the game.

I wonder how many people go through the entirety of the light world before ever starting the dark world. I play it world by world; light then dark and on to the next, always replaying each level multiple times to find the fastest path. I got burnt out before trying Hell Light, but I believe it goes [WORLD (Light then Dark), next WORLD (Light then Dark), repeat] in terms of intended difficulty. I theorize thrashing the Forest on Dark is WAAAY easier than even finishing Rapture on Light.

I have been stuck on the battle/running away from Dr Featus with the crazy saws moving at the sides for so long.