Rhythm-game guitars spent years as the kind of peripheral you bought, wore out and then tried to find second-hand a decade later.
Polybar treats the controller as something you can manufacture instead.
The Three Pieces Controllers project provides 3D-printable parts, order-ready PCB files and build documentation for games such as Clone Hero and YARG. Version 6 added Raspberry Pi Pico support, Bluetooth, accelerometer support and a Hall-sensor whammy setup.
Later releases kept changing much smaller physical details: bearings for the strum mechanism, switch height, press-fit assembly, print orientation and collision fixes around components.
That maintenance history is the interesting part. The controller stops being one sealed plastic object and becomes a collection of parts that can be reprinted, adjusted and replaced.
One important licensing caveat
The project is often described as open source, including by its creator on social media, and the fabrication files are publicly shared. But the repository uses CC BY-NC-SA 4.0, which prohibits commercial use without permission.
So this is not open source in the strict software-license sense. It is better described as a shared, modifiable hardware design with a non-commercial restriction.
That distinction does not make the build less useful. It simply keeps “the files are public” from quietly turning into “anything goes.”
What Polybar demonstrates is the practical value of exposing enough of a physical product for people to rebuild it. Mechanical parts, electronics and documentation become a repair path, a customization surface and, inevitably, an excuse to spend an unreasonable amount of time tuning the feel of a plastic strum bar.