Update #1
After the first week of coding I am quite happy how this turned out so far! Here is some in-game footage:
https://gfycat.com/PertinentDesertedGenet
Camera
Finally, I could use the smooth camera system I wrote years ago in an actual project! I had to port it to an EntitySystem for Ashley though.
Physics
Box2D, naturally. The aliens use simple circle shapes for collision detection, the planet has one as well. I am using collision filtering to keep the aliens from colliding.
Steering
The movement of the aliens is built using gdxAI's Steering Behaviors. The currently active alien uses Arrive to follow the touch/click position, the inactive aliens use Arrive to follow the active alien while simultaneously using Flee to keep them away from each other:
Alien switching
Just a simple scale animation, but good enough for now.
Demo: https://gfycat.com/BabyishTenderDwarfrabbit
The Planet
For now, there is one planet with 8 settlements on it. The settlements continuously produce the "Humans" resource, which can be harvested by the blue alien. There is a maximum number of humans per settlement though. The settlements can be upgraded by giving them "Energy" using the yellow alien. An upgraded settlement produces humans at a higher rate, but further upgrades require more energy. Her are the sprites I currently use for the settlements:
Alien abilities
Yellow alien: Give energy - implemented, but needs some kind of visual effect
Blue alien: Abduct humans - implemented, but also needs a visual effect
Red alien: Laser Beam - TODO
That is all for now, see you all at the next update!