The 2D topic with JME is very interesting.
Using the guiNode node makes 2D games more difficult to maintain, as that node uses pixels and is UI specific, so I don’t recommend making a game under that node.
It is recommended to use rootNode that uses the world scales, as running a game at a different resolution will not warp the models.
I highly recommend these 2 libraries that can help you with your 2D game.
- jMe3GL2D [compatible with the latest version of dyn4j]
- Galago2D [not compatible with the latest version of dyn4j]
Both libraries work in a similar way, with some minimal features that differentiate them, it is worth mentioning that they incorporate the Dyn4j physics engine.
You can take a look at this post, where I developed a game that is in the godot documentation.
[Link]
Dodge the Creeps!