I've decided to continue on the cave flying game, at least for now. Well truth be told, I've spent the entire day just slacking off and reading game design related articles. Lost Garden has an interesting presentation called Mixing Games and Applications. It skims some common game mechanics, so it was an interesting thing to read while trying to decide what kind of levels my game should have, how the learning curve should go. I've never been a fan of tutorials inside games, and reading that presentation made me even more determined that the user should be allowed to discover how to play, instead of being explicitly told what to do.
In my prototype, I can tilt the phone in two axis to move the ship along the X and Y coordinates. In the proto the only activity is obstacle avoidance. If I merely throw the player into this and have different kinds of obstacle courses, that would seem to be quite boring. Instead I should have them on a nice curve where they learn new things and are challenged after each level. I don't think I need to have new types of things on every level, sometimes I'll probably get away with just using older challenges and just increase the speed and amount of obstacles a bit, but new elements should be introduced at times.
I'm even considering restricting movement to the X axis at first, pinning the player to the bottom of the screen. Perhaps I can then surprise them in a later level with the ability to also fly up and down. How to show them that they are now able to move their ship along Y axis without explicitly telling them to tilt their phone, I'm not sure.