Thanks for the interest. Nice to be able to share the results with some people that understand the limitations of the platform.
There is a developer Diary although we had a reboot so most of the early articles are lost. The current is a little less tech then this audience might prefer.
Essentially we run at 1080p 24fps (this is legacy from the original game). We not in the mood to rewrite the whole game balance and logic.
At 1080p we sitting on the following breakdown for performance.
The numbers are in milliseconds.
This is from the following screen shot
We started this project in Java 1.5 at that point we used Java3D to access the acceleration through the Java 2D pipeline. We found that if we connected Java3D to a full screen Java2D context all the Java2D features were in fact accelerated. From Java 1.6 on full acceleration was part of the JRE so we getting pretty good performance.
We have now dropped the 3D game context and work only with Java2D. There are a few tricks. Some of the Alpha composites are slow whilst others fast depending on graphics card. We had to reverse the lighting system since the one composite failed and went to slow mode. Also we use the Translation often for rotations and scaling but never simply scale the corners of an image. We found that often falls back on software.
I think if you test your Java2D right now you will find the performance exceeds your expectations. The thing we doing that's special is more around the streaming of the background layers as the game plays.