Ensure the .jar file is compatible with your emulator. Use Reliable Emulators:

For a long time, Java games (JAR files) were strictly 2D sprites. When Konami introduced the 3D engine for the 240x320 screen resolution, it pushed the hardware of the mid-2000s to its absolute limit.

: If you are playing on Android via J2ME Loader , you can "upscale" the 240x320 resolution and use shaders to smooth out the pixelated 3D models. Comparison: 3D vs. 2D on Java

: Set your virtual heap size between 2MB and 4MB . Allocating too much memory can crash the retro engine environment.