While Fallout and Fallout 2 feature turn-based combat and top-down isometric view in a 2-D engine, Fallout 3 features real-time combat and first or third person view in a 3-D engine. Fallout Tactics and the canceled Van Buren featured both turn-based and real-time combat and a top-down view.
Perks and Traits have been merged. In Fallout and Fallout 2, Traits were chosen at character creation, and were commonly a combination of a powerful advantage and a potent disadvantage, where Perks were purely advantageous.
In the SPECIAL character system, the number of skills has been reduced from 18 to 13, traits have been removed and perks are selected every level instead of every 3 to 4 levels.