Hello folks; I’m the author of Bussard (and also a Pi owner, though I haven’t gotten a chance to try retropie yet).
I have just added a feature to auto-reduce some of the CPU-intensive functionality when the frame rate is low, which should make it unneeded to manually adjust the trajectory as stated above. It’s not available in the alpha releases but if you pull from master (either by git or by downloading the zip from https://gitlab.com/technomancy/bussard/repository/archive.zip?ref=master) you will get that functionality.
The game is still in development and needs more missions to be written, but I am definitely interested in feedback, which I would invite on the issue tracker at https://gitlab.com/technomancy/bussard/issues since this forum here is probably not the best place for it. Especially interested in hearing if there are any other performance problems apart from the trajectory functionality.