ePub / Mobi interactivity crossover—what's possible?

[Stolen]

Hey there!

I've been commissioned by a videogame developer to help them produce a series of storybooks based around their games. The books are approximately 3000–4000 words and will incorporate some illustrations. I've done quite a few eBooks and I'm confident with the formatting of more complicated layouts for ePubs intended for iBooks.

The client is keen on producing a high quality illustrated book, incorporating interactive features if possible (they've got some people with Javascript and Processing experience + others). BUT they also want to hit the maximum number of platforms, including .mobi for Kindle in addition to ePub. I've tried telling them that it's really a choice between iBooks and fully illustrated / interactive storybooks OR going for something less rigid in order to nail all formats, including Kindle.

Truth is, however, that I'm not entirely certain what IS possible. Despite all my research I'm not sure what crossover there is for elements like interactivity and audio between .mobi and ePub and I'm not too keen on wasting all my time experimenting on something that isn't compatible with either as I have other projects to work on as well.

Can anybody point me in the direction of anything that can simply describe what degrees of interactivity are actually possible in ePub and whether there is any crossover for mobi and Kindle's at all? That's all I need to know before I start moving forward with the design process. A chart would be amazing.

Any and all help is extremely appreciated. Thank you in advance!

–DP