This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/5mlP0ti6eNd

1) Print the parts
2) Solder the three LEDs (using the case as a template)
3) Solder the switch
4) Solder the red wire
5) Mount everything in the case
6) Solder the black wire
7) Test everything
8) Fill the case with hot-glue and attach the lid.

9) Use a small bolt or thread to attach the case to the cape.

USE MAX 3.2V AND LED type W5KA412NC (OR USE EXTRA RESISTORS)!!!