How to make an adaptive mobile game?

Hi everyone,

I am looking to develop a simple 'fill the gap' game for the iphone and I would like it to be adaptive, meaning that it can adapt its difficulty level to the player's skill while he/she is playing. It's meant to be used for language learning so the logic is that you give the player a phrase with one word missing and he/she will have to find the correct one from a couple of suggestions. If you know how this could be implemented or have any relevant tutorial/script/example in mind, please let me know. It will be of major help!

Thanks so much!