As I have experienced, the game only runs with the Java 8 version. There are two possible solutions:
- In the source code it is possible to switch (with some modifications) to LWJGL version 3 (https://github.com/libgdx/libgdx/wiki/Starter-classes-and-configuration).
- The jar file can also be run with your own jre (I did that too), plus the whole fun can be packaged into a single executable binary that will work like a simple native application.
Warp: https://github.com/dgiagio/warp
Packr: https://github.com/libgdx/packr
I wrote all this only because I hope that as many people as possible can run this game without any problems. :)