Next, I cut all the wires to length, and stripped the ends. The bluetooth module will actually be held in place by the wiring. It's very light, and there are 9 solid core wires soldered to it, so that's really plenty of support.
The joystick is wired up the same as in the mockup. One side of each button is daisy-chained to ground. The other side of each button is wired to inputs 4, 5, and 6 on the bluetooth module. These correspond to the "Return", "Space", and "1" keys on a keyboard. These already map to commonly used fire, jump, and start buttons in many games, but you can remap whatever game or emulator you're using, if needed. Three buttons is plenty to play pretty much every classic game that you'll ever encounter. Two buttons would probably be enough, honestly, but since we have all the tools out anyway, why not overdo it a bit?
The last order of business is the battery pack. This needs to be accessible so that we can change the batteries. To that end, I screwed a small piece of scrap wood to the side of the lid, then screwed the battery pack to that.
When the lid is on, the pack is "suspended" in the bottom of the enclosure. When the lid is removed as shown in these photos, the pack is held "above" the joystick, so the batteries can be easily changed.
Also note there's a washer behind the pack. This serves two purposes- it consumes some extra length on the screw, and makes clearance for the on/off switch on the battery pack. We don't need that switch, since we have our own, and it sticks out enough to interfere with insertion of the lid in the base.