The Difficulty of Difficulty
The success of the Halo franchise has led to a need to appeal to a wider collection of gamers than just those labeled "hard core." As a result, in Halo 3 the easy and normal settings are easier than they might have been prior, and the heroic and legendary settings are likewise more difficult. Casual gamers will be overjoyed with the easy setting, but they'll miss out on numerous cool features of the game, including hidden skulls and cool enemy AI. Dedicated gamers, the ones who have invested hours mastering earlier incarnations of Halo, will want to jump in on heroic or legendary, lest they risk becoming bored from the start.
The secret skulls were first included in Halo 2, but then they nearly always activated some challenging feature, such as not being able to see anything on your HUD. In Halo 3, the system of skulls is much more challenging (read: fun) for anyone choosing to find them and activate them. A skull might make it so you can't see your gun scope, or enable enemies to throw grenades faster. Activating a golden skull makes the game harder for the player, but by surviving you earn a lot more points.
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