The D3 heat map project shows the monthly global land surface temperature average. This project was the first D3 project where I didn't have an exact tutorial to follow along with so I was pushed out of the nest a little bit and forced to fly on my own.
The colors of the chart cells is controlled by how much above or below average the temperature was for that month. I took the conditional coloring I did in the bicycling scatterplot a step further and had more than just two color options.
The thing I remember having the most trouble with was figuring out how to center the months axis on the left hand side of the chart to the middle of each block rather than at the top.