This was largely an aesthetic project and an exercise in designing within constraints. The main constraint was: everything needed to fit within my KDBfans carrying case. I wanted to build a companion brain (I mostly used it as a glorified Bluetooth transmitter) for my Frozen Llama Ducky keyboard as well.
The battery compartment uses a flexible PLA shield that can be stowed under the battery compartment. I wanted to emulate the lines that old Atari and other retro computers and consoles have. The original battery compartment used 3x18650 cells in a modular battery holder, but I ultimately decided to design for 21700 cells to make room for the UPS.
Shout-out to @atltvhead for pushing me to enter into this contest. You can see his entry here: