I saw a Youtube video along time(can't find the video anymore) with someone using capacitive buttons. I found the github for the project but I didn't just want to copy it. https://github.com/fb39ca4/kappa-pad
I wanted to use the Atmega32u4 for this project and the Arduino Pro Micro is perfect for this project. I bought the Pro Micro on Aliexpress for $2.98
Step 1: Designing the PCB
I have access to Altium Designer so I used that. I bought twenty 100x70mm single sided boards for another project and wanted to use them. I also wanted a ISP plug on it to program the Arduino ProMicro just in case I brick the Pro Micro.
Step 2: Making the PCB
I tried making the PCB with a CNC wood router but both the board and the router bed was not straight so there was some areas where it cut too much and another that didn't cut any.
I then saw an Instructables on how to make a PCB with a laser cutter witch I also have access to.
I also etched with Vinegar.
I made sure that it is completely etched by shining a light thought from the bottom and reminding copper will block the light.
Step 3: Soldering
Once I finished etching, I solder the Pro Micro by elmer gluing the middle of the pro micro and lining it up on the PCB. I then put the tip of the soldering iron into the Pro Micro's holes and flowing solder around the tip. There were a few trapped air inside in a few so I had to tap the soldering iron into the hole a few times to release the air.
I then soldered the tiny 0805 resistors and leds.
Step 4: Finishing
I kept the black paint on the pad from the etch process on but I believe that the etching process weakened the paint a bit so after a while from playing Osu!, the paint started to come off. I then removed all of the paint from the pads using acetone and painted it with clear nail polish. I tried giving it two coats but the nail polish clumps up and doesn't really want to go on dry nail polish so I requirement using only one heavy coat. I also taped a piece of wire in between the pads so I can feel if my fingers are drifting to the other pad.
Step 5: Programing
I took the code from Amar's KappaPad and modified it making it simpler and some other things like disabling the TX and RX leds and changing the pins to match my pcb.