Place the Circuit Playground inside the case bottom to be sure it fits and snaps neatly down onto the three pillars.
Remove it, and thread all the wires through the hole on the side of the case.
Solder all the wires in place according to the wiring diagram. You'll have 2 wires going to BATT, 3 wires going to G, and two going to pin 9. There will be one wire each on 3.3v and pin 10.
Note: It's a bit of a tight fit in the case, so it works best to solder the wires from the TOP of the Circuit Playground rather than the bottom.
Plug your battery in, switch it on, and be sure everything is working properly.
Slide the horn through the hole in the top of the hat and sew it in place. Wrap the threads around and between the light pipe strands rather than piercing them with your needle.
Finish by stitching any holes in the lining closed so that all wires are hidden.
Put your hat on and listen to the left. Listen to the right. Can you hear the magical rainbows all around you?