ungie has said co-op difficulty in Halo: Reach will be scaleable.
According to Brian Jarrard, speaking to
Kotaku, enemies will get harder when there are two or more players involved, when compared to solo-play.
Previous Halo titles required player groups to manually increase the difficulty level for more challenging gameplay, but Reach enemies automatically get tougher and smarter for each player in the group.
Good to know.
Bungie announced at E3 that Reach would contain Space combat, and to make up for the mode’s
lack of multiplayer the popular Firefight mode from Halo 3: ODST
will be included.