I don't know about a 4 inch screen, but if any AAA shooter can work on a 7-10 inch screen it may be Bioshock given the tight spaces most the action takes place in. Even Uncharted Golden Abyss, which was created specifically for the small 5 inch Vita screen got to be a pain in many places due to the longish draw distances and the teeny, tiny enemies off in the distance Nate had to shoot at. In fact, it seemed just every other shootout area provided the player with a sniper rifle with adjustable scope to get through it. Bioshock can even be played using melee combat almost the entire time if you upgrade properly and use the right tonics. Who would buy it is anyone else's guess. Maybe Apple plans a decent marketing campaign.