iOS 4.2 is available and now I can update Emerald Run for iPad! I had already created infrastructure for this previously but had not enabled it. The update will be free.
Also, some minor shader tweaks on iOS 4.21. Apparently, if you have a unused varying variable in your vertex and fragment program you get a link error! Fortunately, if I get a shader compile or link error, the program will always fall back to something I call the bumper shader. I always make the bumper shader the simplest shader possible -- just making a blue color with no shading. One of the drawbacks of glsl in general is that it can puke in different versions of the OS and hardware depending on the driver implementation. I would emphasize lame pc video cards, for example, as being unreliable in general. But the point of a bumper shader fallback is to ensure the app does not crash badly which it did not in this case. So, blue brake lights and blue radar dots -- fixed in the update.
Also, I put in some minor fixes n' tweaks with regards to rotation and physics.
Future focus will probably be on shader optimizations and ai .
Uploaded the new version of Emerald Run to the App Store tonight.