Hey! Glad you liked it. I rewrote rendering part of the engine several times to achieve smooth fps. It wasn't an easy task even for a simple game like this.
Stick requires full options implementation for an ability to disable it because both of my PSPs have drifting issue. This was the main reason why it is disabled. It's actually there in the code just commented out.
I planned on settings and some more stuff like map editor if game will become at least slightly popular but in the end I abandoned such ideas on improving anything and moved on.
About sources I'll think about it. Releasing sources of PSP version without graphics might be ok with me. I'm just unsure if anybody really will try to do something with them. Can't say I really invested into good architecture and code of the engine.