The second attempt was a huge success! I was only planning to get through the soldering but I had so much fun that I finished the full assembly in one night. @epk I didn't realize desoldering was even an option on my first attempt, but it made the whole thing much less stressful.

More open-source hardware kits, please. I originally found the Ploopy mouse when looking for trackball mice with high-res sensors and a thumb scroll wheel. My right hand often hurts from scrolling with my pointer or middle finger so I've been searching for a solution to that for a long time and I think I've found it. I love that, like my keyboard, it's something I can repair or modify myself.

If you are in the market for a mouse (or headphones!) check out their site. I'm now a fan.

Here's a photo of the finished product: