In the last two days I worked on some graphics and movement stuff.
I have animated the graphics for the sources: rather than being blue dots, they are colored with their power type with an outer and inner circle. Between them a number of dots equal to the power of the node circle the center.
Problems with that: sources dropped from sites have a background of the same color, rather than the underlying ground (which I've modified the sources to show; hopefully walls do). As I understand what I'm doing, I don't think this should be happening and I can't identify the source of the error.
I have also colored the sites and creeps. Creeps of different color now have different numbers of hits and different speeds. A creep with more hits does more damage to walls and things.
I've also changed the movement to reflect the underlying ground. This makes the creeps' paths make sense. Unfortunately, since I've hacked the Uneven_Ground pathfinding to reflect the presence of walls and sources, when a wall is destroyed the creeps move too slow through the previous space. To fix this, I will have to start writing the actual AI code. I can't start optimizing the code yet, though, because there are no trade offs for length of path incorporated into the game, yet.