@pvg I'm glad you enjoyed it! We used libGDX as our game development framework, with gradle as the build management tool (standard for libGDX). The assets were created as vector graphics in Inkscape by my partner in Inkscape, and the music and sound effects were created by him as well.
The game uses Box2D physics engine at the core, by defining Earth as a centered Staticbody and each satellite as a Dynamicbody. Our game then manually computes the gravitational pull vector and applies to each satellite at each time step to simulate the gravitational pull in an orbit.
The most time consuming part was modifying the initial impulse when launching the satellites, as well as an initial 1 second thrust applied to them, based on the launch angle, such that most launch angles place the satellites in an orbit, as the game would otherwise be way too difficult.