It also works with USB gamepads!

At DEF CON where we will have this set up in-person tomorrow, we will have people playing on a USB Dance Dance Revolution floor pad.

What an amazing idea.

Another thing to make the entry easier: Create a "Memory" label for the memory area. You mention it in the intro text but color it in the R12 address color which was confusing for me.

Missed that memory space totally while playing the first two times.

Cool! Does that use the Gamepad API or WebHID? I'd like to get one working in the browser for one of my projects

Uses the Gamepad API. I found it very easy to work with, in large part thanks to the corresponding MDN docs.

The only weird part about the Gamepad API is that you have to poll it rather than handling events the way you normally would for other, similar stuff in JavaScript. In practice, this means that you have to do your own debouncing for handling things like key combos, but that doesn't really affect individual button presses too much.

Magic, thanks! Which model mat do you have?

It might be worth trying with WebHID instead of the GamePad API. Quick example with a joystick :)

https://murkle.github.io/utils/webhid/logitech_attack3.html

... and a quick example with a very cheap USB Dance Mat https://murkle.github.io/utils/webhid/dance_mat.html