Little article I wrote after the creator posted to our Facebook group earlier today. Very cool, but you'll need an SD reader to transfer the file to your VMU. http://www.thedreamcastjunkyard.co.uk/2016/03/flappy-bird-now-available-for-dreamcast.html
It's very neat, although the physics isn't the same as the original flappy bird (and REAL LIFE): https://fnoschese.wordpress.com/2014/01/30/flappy-bird-when-reality-seems-unrealistic/ For a second version maybe
You can embed this into DreamExplorer then toast a disc and transfer to the VMU just gave it a go myself on my AA battery modded VMU and it's still tough as nails. While not as hard as the PS3 variant (only one I played) it is still fun to play and great to see development on Sega's ole pocket system.
I'm surprised you fit AA's in there and it still fits in the controller. Is there a link you can point me to? It would be cool to see this thing.