Here's a landscape / flight simulation engine that I have been playing with. I'm still figuring out how to turn this into a game, but at least it's functional now and runs at 30 fps.
It takes a few seconds to generate the map using simplex noise mapped onto a sphere.
Controls:
Arrow keys to turn and pitch up and down.
Z-key to accelerate
Notes:
There's a 3D shaded polygon engine built into this as well, but I'm not using it yet.
Thanks Anthony DiGirolamo for the simplex noise:
--https://www.lexaloffle.com/bbs/?pid=32443
--ElectricGryphon