i have the same problem. i downloaded it and extracted, click on the dragon to start the game the screen goes black like its going to start then goes right back to desktop screen with nothing running. so, the error file in the folder says here
Uncaught exception from thread:Thread[LWJGL Renderer Thread,5,main]
java.lang.UnsupportedOperationException: GLSL and OpenGL2 is required for the LWJGL renderer!
at com.jme3.renderer.lwjgl.LwjglRenderer.initialize(LwjglRenderer.java:166)
at com.jme3.system.lwjgl.LwjglContext.initContextFirstTime(LwjglContext.java:131)
at com.jme3.system.lwjgl.LwjglContext.internalCreate(LwjglContext.java:168)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.initInThread(LwjglAbstractDisplay.java:128)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:205)
at java.lang.Thread.run(Unknown Source)
Application was not initialized.
so there you have it thats my issue and i WANT TO PLAY IT!!! im dying here!!! lol
You need to check your drivers to make sure they are up-to-date, or your graphics card may not support mythruna.