you have to complete all the missions to beat the game (there's 98 of them, not counting the postgame ones) and it's as fun as it sounds. 90% of them are extremely simple and boring, but some of the last ones are extremely hard and frustrating. this game doesn't add anything to AC2's formula, but it did remove the arena tho. It's an all around boring and unnecessary experience, unless you reaaaaaally loved AC2 i guess