A basic Adaptable Game engine library(BAGEL) wrote with javaFX, learned from Lee Stemkoski. (http://www.stemkoski.net) (https://github.com/stemkoski)
This engine is basic, but highly adaptable. you can add few methods and build awesome simple games.
some features to point out :
- it is written with AnimationTimer class, so you basically have no limit in updating scene.
- it can handle animations by loading sprite sheets.
- it's got a Physics class that is written in a way to accelerate moving objects, with customizable amounts.
- the code is in standard situation, where you can see accurate inheritances.
- for being adaptable as much as possible, class fields are mostly public.
also the code is highly commented.