Tip: In the area with the collapsing platforms over the lava, 2 things.
First, the platforms don't collapse from stepping on them, but instead there are hard-to-spot switches on the black strips that cause them to collapse. Don't touch the switch and the platforms don't fall.
Second, if you, like me, tripped the switch at the start of the area and made the ladder impossible to reach, don't worry. It isn't impossible. If you avoid collapsing the platforms to the sides of the ladder platform, you can perform an unarmored run and jump to reach it. Don't freak if you die in the attempt, I very nearly rolled off the other side of the platform.