For more information about adding or modifying maps entities for COOP or DIE, read this discussion.

If you want your modifications being published online for all players, please follow these rules:

• Don't remove previously added contributions, or give a good argumentation and remove the minimum.
• Before sending your xmlrule file to me, send it to another player who should test it (I won't have time to test all files).
• Don't add monsters that should attack the player at start, just after spawning.
• A good idea is to add more ammo, because in multi-player there is a lack.
• Another good idea is to add monsters, because it's fun, but respect the level of difficulty, only add monster type already available on the map, or just a level higher.
• Another good idea is to add easter eggs, like the dead body near the elevator in the first map.
• If you add weapons, be careful to not change too much the gameplay. I think a good rule if you add a powerful weapon in a secret place, early in the game, put it only one map before the map where it should be normally found.