I just realized.  Apparently I never uploaded the hardware source files for this.  Wow, how time flies.  

I do remember 7 failed branches of ideas working towards a print-flat, pop through, TPU button, and finally one 'good one'.  

I'll get at least the good one uploaded when I sort out what is what.

<EDIT>

Found the latest OpenSCAD source, updated the Readme.md and files with license information, and pushed it up to Github.

This version added a cutout for a Dotstar module to shine through from the bottom.  This eliminated wiring within the button itself.  Also, placing the module inside the button made for a rather unattractive point light source, whereas putting it below gives it a larger distance to spread out.  

There may have been polyester fiber-fill involved as a diffuser, but I can't remember which worked better.  Experiment!!

In any case, the dome shape and disc get covered in AL foil with spray glue, and a sheet of non-aluminized mylar (gift wrapping plastic) placed between them for use as a dielectric.  

This formed the capacitor that the Teensy could read.  Pressure applied to it would deform the dome and increase the capacitance.  It was still more of a log() curve than linear response and perhaps some scaling is in order.

</EDIT>