Laser Cutter Build Night: Video and Improvements

I finally got around to taking a video of my laser cutter base in action!  I wrote a simple script in Python that moves both axes both directions (one at a time) and then flashes the practice laser diode.  Notice how I have to use Blogger's video capabilities instead of YouTube because they shut down my account (I have gotten no word from them as to why my channel was shut down).
I also added some improvements to the electrical system.  As seen in the video, I can successfully control the laser diode with my Raspberry Pi.  I used a random NPN transistor I salvaged from a rear-projection TV and placed a 1K resistor between the transistor base and the Raspberry Pi GPIO output.  This time, however, I powered the circuit off of my lab power supply at 12V.  It worked great!  I added another 12V splitter cable off of the main laser cutter power supply to eventually power the final laser circuit (I need to test it with the real DVD burner diode before I make it permanent).  Additionally, I soldered a computer case fan to the whole mess of wires to cool the EasyDrivers.  The electronic control system will go in a box with the fan on top, eventually.
Regarding the backlash along the Y-axis, I am leaving that be for now.  I adjusted the threads on the sled but that didn't help, so I will compensate for the backlash when I code the laser cutter program.  I plan to add a backlash variable and then make the laser cutter draw a square - if the lines of the square don't close off, I can adjust the backlash variable and re-draw the square until the lines meet.