UC Berkeley Starcraft Class, Week 2

Week 2 of the class was better than week 1 because most of the administrative stuff was out of the way so more time could be spent discussing StarCraft itself.
This week was about units. Professor Feng started by explaining that units are your eyes, ears, and hands in the game. Units give you vision through the fog of war (eyes) and are they are what you use to perform actions such as attacking, repairing, building, moving (hands). What he said we might not realize is that they are also your ears. He mentioned one match where the famous player Boxer put an SCV kind of near some minerals to scout, but it was actually the sound effect for gathering minerals he listening for, rather than the sight the SCV provided.
The next topic was something I refer to as local imbalance, though that term wasn't used in class. Explained in my terms, a game is supposed to have global balance (Zerg vs. Terran for example) but it's supposed to NOT have local balance, or it would be too boring on homogeneous. StarCraft has massive local imbalance amongst units and that is a very good thing.
One example was siege tanks. The longest range Protoss ground unit is