code/__DEFINES/overlays.dm 
| MAX_ATOM_OVERLAYS | A reasonable number of maximum overlays an object needs. If you think you need more, rethink it. |
|---|---|
| VALIDATE_OVERLAY_LIMIT | Checks if an atom has reached the overlay limit, and make a loud error if it does. |
| POST_OVERLAY_CHANGE | Performs any operations that ought to run after an appearance change. |
Define Details
MAX_ATOM_OVERLAYS 
A reasonable number of maximum overlays an object needs. If you think you need more, rethink it.
POST_OVERLAY_CHANGE 
Performs any operations that ought to run after an appearance change.
VALIDATE_OVERLAY_LIMIT 
Checks if an atom has reached the overlay limit, and make a loud error if it does.