I'm creating a fireplace whereas I'm using a projected texture for casting shadows. To make it a little bit more realistic I wanted to make the projected texture to move inside the fireplace at random positions, in a small area. I tried to parent it to a func_door, and sure it works but it just moves in a line. What else can I use to parent the projected texture to? Thanks in advance!

a func_tracktrain that follows some sort of random series of path_tracks?

It is indeed possible to put the projected texture to random paths. Using a logic_case pickRandom output you can direct the func_tracktrain to a series of path_tracks or teleport point which specifically teleports the projected texture entity.

Thanks guys, however I'm sorry to say I'm kind of lost. I've checked the entities you recommended and read about them but I don't even know where to start. I don't know any other map which use these entities either. Can you help me with the specifics how to set this up? Appreciate your help so far!

Path_tracks basically define a "rail" the tracktrain will move along. The best example is Wheatley's management rails. In this case, you'd want to put down a bunch within the fireplace, with slightly offset angles. Give them names in sequence (like track1,track2,ect). In the first set the "next stop target" keyvalue to point to the second, and so on (if you shift-drag one hammer will automatically increment the number and set the keyvalue for the original track.) Set the rotation type to use the path_track's angles.

For the tracktrain, make a 16x16x16 nodraw block. Set the "first stop target" to the name of the first track (it teleports here on spawn). Set "height above track" to zero (otherwise it will actually appear higher up). In the flags you want to set "passable" so it's non-solid.

For control, you can use the StartForward/StartBackward inputs, but I think the logic_case would work better. Make a logic_timer with "use random delay" set to yes, and give it a suitable max/min delay. OnTimer make it tell a logic_case to PickRandom (which makes it choose a random OnCase__ output that has outputs specified). For each path_track, make an OnCase output to tell the train to MoveToPathNode with a parameter of a path_track. Do this for all of them, so it will randomly move between each one. You could instead use TeleportToPathNode to make it instantly move to each, which could look better.