Sorry the late reply...
We don't use an engine as such, this is all C with a custom framework for the NGPC.
There are downloads and a few tutorials on my site at ahchay.com
Really lovely little bird animation - reduces down to 3 colours nicely
Don't forget to change the default frameskip setting in neopop - by default it starts at frameskip 7 or something
Hard mode gets a bit hectic as you go on, but we're pushing against our sprite budget all the time and if we go any faster it all gets a bit juddery I'm afraid
We could maybe put an option to start at the highest zone reached
You're very welcome, and thank you for supporting us
Thank you, we're very glad you're enjoying it
No, thank you for playing and enjoying our little game