combat system help
obj/Weapon var/Worn=0 Click() if(Worn) Worn=0 usr.overlays-=src else Worn=1 usr.overlays+=src
http://www.byond.com/developer/Forum_account/EnemyAI <-- This may be what you're looking for.
That's a small example of how to add overlays.
Anyhow, I'd advise you to read the DM Guide ( http://www.byond.com/docs/guide/ ). Doing so would help you drastically.