Reduce framerate drops when testing on mobile device

[Otterlord]

When testing Jetpaca on my android device, I experienced frequent framerate drops and lagging. I think this is due to the (relatively) large amount of physics objects being accounted for in the game, combined with gdscript being a bit slow.

I was testing with 5th generation Kindle Fire, if that's relevant.

[ObaniGemini]

Note that this project isn't really maintained anymore. If you feel like forking it or joining the team to help on it, I think we'd be glad to invite you. Many of the bugs you spot are tiny works but that need to be done by someone. Also, the game has lots of unused potentials left from its original makers.