Update 9-29-15-2.0: Adding photo of "tapped" mouse at the bottom.

Update 9-29-15: Adding schematic at the bottom.

Wanted to get the whole system running and make a video of the whole shebang for the "reveal", but decided it's too cool as-is :)

So, there's an old ball-mouse, its phototransistors and buttons have been "tapped" to feed directly into the system's circuitry. The circuitry consists of nothing more than two Dual H-Bridge chips (designed for bipolar motors, from old floppy drives), a couple transistors to switch on and off the laser-diode's circuitry, and a few LEDs, capacitors, and resistors. No software! No microcontroller!

As far as mouse-hacking: I didn't even bother interfacing-with (nor even removing) the original PS-2 microcontroller from the mouse; just tapped off the signal inputs right at the microcontroller. This could be quite the handy tool for later experiments and early-phase projects, as well.

Later, I do intend on controlling this via computer, to literally "burn" images onto floppies. I've looked into backlighting, a little, possibly strobed to create a zoetrope. And a multitude of other crazy ideas, including audio-storage ala CD, but with visible "pits." Who knows...

Here's the schematic:

Here's the "tapped" mouse... I followed the traces to the built-in microcontroller, it could be physically removed, as it's not being used, but it was an easy solder-point.