Bungie has said that Halo: Reach will feature scalable difficulty in co-op.
According to the studio's Brian Jarrard, speaking to Kotaku, enemies will toughen up when faced with two, three or four players rather than a lone Spartan.
In previous games, groups of players would need to increase the difficulty level manually to make the game more challenging, but in Reach the effect will be the same - also meaning that higher difficulty levels will be even more difficult.
Along with a sizable campaign starring a group of Spartans on the doomed human colony of Reach, the game features rethought multiplayer and an updated version of Halo 3: ODST's Firefight mode.
Halo: Reach is due out on 14th September. It's Bungie's last Halo game. Sniff.