hi... i need some help with my TD map. How can i create a unit that won't be able to move. I want to know how the creator of Random Beacon Defence did.

1. create a 1x1 location called 'freeze location' and put it in the right lower edge of the map.
(in general the location has to be put over unwalkable terrain like water or space)

2. a trigger system like that

modify men to allow some units to move like an scv. just make this trigger action for every unit which should be freezed.

3. use hypertriggers (explained here)

effects:
-units are not able to walk
-units can attack
-units can cast spells
-units are nearly unhittable/invinceble

if you want to freeze air units, you need to put the location out of the map. (Other methods can cause lags)
(resize map to 256x256; move location in the right lower edge; resize map again)

thanls a lot i'll try it right away

Where are you getting that? Moving the air unit to a floating CC doesn't lag..

moving ground units to walkable ground which is already filled up with ground units cause extreme lags (I nearly freezed the game with that ;P). why it should be different with air units?

Only a few units will not cause lags, but if you freeze many air units, it may lag.

Hmm, I guess that's true, but that's only if you're trying to move LOTS there, most people are only trying to stop a couple units.

so I wrote 'can'

SO let me get this straight. when you try to move the unit to a place it shouldnt be able to go its stuck in a impossible loop and just..cant do anything?

try out my map and you will notice most of the effects...