I went with EasyEDA for the design, because I'm trying to move away from Fritzing, but I still can't stand KiCad. Plus I get all those footprints for free. The basic PCB was done in a single evening. I drew the body using a graphic tablet, imported it as the silkscreen layer, and made the board outline and all the rest manually.
It took me a while to figure out the positions of all the components on the back, especially the battery and the Xiao module. Initially I tried to use a coin cell battery, but the people on the badgelife discord talked me out of it. I ended up with a 14250 lipo battery, and I put the battery holder over the module, so that it can act as a backpack.
Electronics wise there is the display, the Xiao module, the battery with a power switch, two LEDs on the gun, and a LIS3DH accelerometer chip. Oh, and a transistor to do power switching between USB and battery, but since I plan to use the Xiao ESP32-S3, that already comes with its own power circuit and battery charging, I will just short the pins on the footprint.