You should be able to use triggers to make all players treat each other as allies. Also, if you make everything invulnerable and make the weapon exclude invulnerable targets it should work as well.
However, towers might shoot at an allied player's waves.
You should be able to use triggers to make all players treat each other as allies. Also, if you make everything invulnerable and make the weapon exclude invulnerable targets it should work as well.
However, towers might shoot at an allied player's waves.