Oh, if you squint you can make out a tiny blue blip (your character) and a yellow one (the position of the light source). Next up, I'll modify the algorithm to calculate shading per vertex instead of per face. I'm hoping that makes it look lots better.
If you're wondering why this looks so much worse than the previously posted image, it's because the previous terrain just assigned darker colors to lower points and brighter ones to higher points. Cheating!