Stabyourself.net
As part of the huge customization we add for mappack authors, we are also adding custom enemies to the bunch.
You’ll be able to create enemies with custom graphics and behavior by including sprites and then setting a bunch of properties for your enemy. So basically you can tell the game your enemy is “stompable”, but “killsonsides”, then give it the standard movement property (“truffleshuffle”) and you got a goomba.
I was messing around and made goombas throw goombas like hammerbros.

The following properties were used for this:
spawnsenemy = "goomba",
spawnenemydelays = {0.2, 0.1, 1},
spawnenemyspeedx = -15,
spawnenemyspeedy = -20,
So yeah, we’re pretty excited about this as it opens up a lot of possibilities for map creators.