Sonar Bat

This game is pretty similar to Flappy Bird (as I'm not creative and new to programming), but after a couple obstacles it gets dark and you have to navigate just with the help of you bat sonar.

Linux and OS/X build not fully tested, but should work (jar-files)

If anyone more experienced with programming could give me some constructive criticism on my code, that would be nice.

Controls:
LMB: fly up
F12: take screenshot (generates Screenshot folder on desktop)

Edit: Added Source