If you look at the source code of the Desktop App, you won't find any code that deals with the heavy backend computations. That is because that backend code is contained in a separate Java framework for Particle Life. The source code is available on GitHub and can be installed via Maven or Gradle. This means that you are free to build your own frontend for Particle Life, not having to wory about optimization of the backend computations. For instance, you could easily write an Android app using this framework.
Contrary to what the name suggests, you can simulate more than just Particle Life with this framework. Have a look at the Accelerators section to understand what possibilities you have with the framework.