I bought the Adafruit Space Invader pendant but I didn't want to just dangle a PCB on my neck, so I made this. You can follow the project on Adafruit's site for all instructions for the electronics. Just print this case off and put it together. Beginner-friendly. Print the battery holder with supports. Print everything else without supports but you may need either a brim or printing disks (put these at the pointy parts) because of the sharp corners (which may pull up off your bed if it's not heated). Top and bottom snap together but you'll need a couple of small screws and nuts for the battery holder. Optionally, change out the JST connectors for something more rational. Finally, I made mine without a switch and just programmed it to loop forever. To get it back apart, just squeeze the bottom part and pry it apart. Program your Gemma before you put it together and you won't ever have to take it apart (provided you've used alternative JSTs) unless you tire of the animations. To ensure proper orientation, mount it so that what would normally be the necklace part if you were just dangling the PCB is pointing towards the small necklace holes, or away from the big battery hole. The big battery hole goes at the bottom. There is enough room inside so that if you don't get the wire lengths quite right, it'll be fine. You may need to stick one piece of wire underneath the opposite side of the backpack so that it sits evenly (you'll understand when you do it). The circuit board assembly will move around slightly, especially if you push it in.  You can stop this by taping it or putting something non-conductive behind it, or just readjust as necessary.