Demons are scary

but they can't navigate stairs worth a darn. What's the magical formula? it seems that the height of each step may be a contributing factor, and maybe even the direction of the steps? As in vertical/horizontal vrs diagonal?

NT

It's to do with the monster's total move distance per step. If moving forward at normal speed would result in a larger-than-possible (>24 units) height change (regardless of what lies in between), the move doesn't happen. So if a monster is on step A and its next move would place its radius within step C (effectively skipping B altogether), then the move is not made if the vertical difference from A to C is greater than 24 units. This happens often with demons moreso than many other monsters since they're wide and move quickly.

I'm too tired to do the exact calculations in my head, but I do know that, as an example, Demons won't climb 16-unit-high steps that are spaced 16 units apart.

This is something interesting to note: reduce their radius by a wee bit, and they'll fly up stairs, through doors, and around tight spaces like a nightmare. I did this in an old mod and it made the demons much more threatening, especially with -fast mode or Nightmare difficulty. It has the side effect of making them a bit harder to hit, but it really adds to their ability to maneuver, a good trade-off.

Their goatlegs make it difficult for them to walk up and down stairs.

Is it a design mistake or was it an idea they got from watching Robocop?

Make stair cases longer.

GeckoYamori said:

Is it a design mistake or was it an idea they got from watching Robocop?

It's most likely a monster design shortcoming, which they probably decided to keep.

NaturalTvventy said:

but they can't navigate stairs worth a darn.

Demons are daleks?