Enhancement request - Bits indicate on/off as a light

[fredsherbet]

I created a countdown timer, and was showing my kid how it works. I got very confused remembering which direction was "on" and which was "off" for each of the bits. I'd love to be able to label up the parts/directions, or even better have a read-out of the bits.

I realise this is rather extending the scope of the simulator! But would help understand binary, and help when configuring the board.

Thanks for creating this simulator - it's helped me encourage the kids, while we wait for the real thing to turn up!