Gimbal

Mechanics are simple enough that a 9 year old can play it but with "Mastermind" class available the ceiling is virtually endless which is only cap by your understanding how to build a ship and your eyes to see witch pixel has extra spaces for parts XD.

Using a nice creation suite, you create your own little Fighter by dragging and dropping, rotating and such of individual modules - pieces of steel & armor, wings, weapons, energy/engine related parts...

Another good thing about Gimbal is the option to host your own server, add bots to it (This allows for Co-Op and solo play) and to adjust almost any setting to your liking.

The 2D visuals are very appealing, but offer a welcome retro look reminiscent of space shooters from an earlier gaming era The similarities end there, however, Gimbal has realistic physics, a large arsenal of guns, thrusters and upgrades, and really allows you to make it whatever game you want to be with different player modes like capture the flag, racing or traditional team vs team combat.