There's rules!

Falling one block distance is safe. Falling two blocks or three blocks kills you. Falling three or more blocks doesn't kill you, and you'll learn this naturally as you progress, usually in the room two to the left of the February 14 Valentine's Day room.

You can jump up through thin platforms and can walk through certain passageways hidden by foreground objects, most notably any thin pillar-like structure such as those in the first room of the caves with spikes.

The other things you'll learn by experimenting and noticing areas of particular height. If you can get enough height before landing, you can sometimes change the outcome of your fall.

There's also a couple of diagrams you can find on walls that help you locate things. Two of these indicate a place you can enter that's a secret passage, one helps you with checking what happens when you fall certain distances, and one is a map that updates as you collect pages in other rooms.

Great, thanks! The falling and bouncing thing threw me: I thought this was only possible in predefined places, like a hidden trampoline. It makes sense in hindsight.

Originally posted by Thirith:

Great, thanks! The falling and bouncing thing threw me: I thought this was only possible in predefined places, like a hidden trampoline. It makes sense in hindsight.

yeah it's not a coincidence that you are bluntly taught to press shift to show grids one room prior, plus your character is color-coded for this change during the fall (with achievement highlighting it), but people don't always make that connection and can easily overlook the detail of color, or might have turned off achievement note and miss that clue.

Perhaps I would've fared better without COviD brain fog... but probably not. ;-)