It's based off this model on Thingiverse I scaled it up to 110%, removed a few buttons to make it easier to use for my son, and created a new battery holder for the 4 AAA's that power it. I decided on an Arduino nano as the brains with a cheap LCD for display. Again, not going for screen accurate but something that will keep a 6-7 year old entertained. I did program in the Ghostbusters 2 LED pattern for the wings.
The big trick to all of this was getting the electronics to fit in such a small place. I build my own PCB from OshPark for the LED driver board/5v rail to power everything. This worked out pretty good.
it took me about a month from start to finish to build this. I'm really pleased with how it came out. All told it cost me about $50 for materials and parts to build it.
Now I'm starting in on a proton pack for him. Sure hope I can get it all done by halloween