Say I have a game that runs full-screen on iPhone 4S and older devices. The balance of the game is just right for the 480 x 320 screen and associated aspect ratio. Now I want to update my game to run full-screen on the new iPhone/iPod Touch where the aspect ratio of the screen is different.

It seems like this can be challenging for some games in terms of maintaining the "balance". For example if the extra screen space was just tacked onto the right side of Jet Pack Joyride the balance would be thrown off since the user now has more time to see and react to obstacles.

Also it could be challenging in terms of code maintenance. Perhaps Jet Pack Joyride would slightly increase the speed of approaching obstacles when the game is played on newer devices. However this quickly becomes messy when extra conditional statements are added all over the code. One solution is to have some parameters that are set in once place at start-up depending on the device type.

What are some strategies for updating iOS games to run on the new iPhone and iPod Touch?