Secret_Tunnel said: is there a natural next step to learning how to sequence break this game?
Might not be what you want to hear, but I would say the next step is GameFaqs haha.
The 15% run pretty much runs on sequence breaking and they can be tricky as hell to find. You could spend ages looking for all the right spots and plotting out the ideal run....or just follow along.
Half the challenge is actually *beating* the thing with an abysmal amount of health ammo and abilities, so I didn't feel too bad about having the guide to help things along.
That of course being said, if you're going for all 8 endings, maybe leave those two until last? They're super tough, and it might help to become more familiar with the game through the speed running and completion endings.
Of course the other way to look at it is, if you can take out the game with 15% completion, the other endings will be a cakewalk at that level of skill. Up to you.