General Topdown Mapping

Topdown mapping is not much different from mapping for regular Half-Life either, all you have to think about is that the player will be seeing from the top. (See camera in picture)
The camera distance is definable with a trigger_set_camera, but it defaults to 256 units. So, the player will be seeing everything 256 units up from the player entity.

You can use small monsters such as headcrabs and snarks. In topdown mode the player will be able to hit anything while ducking.