@ Futurulus
Here's a visual

Ignore the numbers, that's for debugging issues.
As you can see, the entity is standing on a vertical wall as you have mentioned.
I'm trying to let it rotate about its z-axis. I got that part working correctly but say when I want to run up the ceiling or back at the floor. Then the angles will change due to ang_rotate giving an incorrect motion. But I think I'm getting close to a potential solution

@ Grafton

Thanks for the demo but I was already aware of this as well ^^
Quaternions are indeed the answer but I don't want to use them since I trying to create a wallwalking/ceilingwalking system which only uses 3dgs native angles (Euler).

@ Rhuarc

The downside you're talking about is also one of the problems. I've thought about using quaternions only when the tilt value of an entity equal 90 or -90. So when other tilt values are reached, using Euler's angles. But it's process intense like you mentioned thus using it only for that reason would be unlogic

@ vlau

Basically, I know all those topics since this past week, I've spend hours in searching for a solution on this forum. Some were helpful like the one you've mentioned But the only problem is that this code from the manual takes a direction vector into account which is the camera. Since my code is based pure on angles, I can't really use it ^^
About LC, I'm actually more a c-script fan

Thanks again for all of your input

Thanks in progress

Frazzle