EPTFirst, allow me to explain the rules. Assume you have B- micro/macro.
You have several factors that judge how your game works.
Income-Your Economic Strength, judged by worker count and number of expos. 10 is a fully operational base. Depending on your income, there will be effects on your unit count, production, and income.
Production-The buildings that you have for production. Based upon your income, and will effect your unit count.
Unit Count-The amount of units that you have. This is your combat strength and determines your ability to attack, harass, and defend.
Technology-Dependent on income. Tech Level 1 is assumed to be Barracks/Academy, Hatchery Tech, and Cybercore. Tech Level 2 is assumed to be Factory/Starport, Lair Tech, and the first group of Protoss Advanced buildings (Robo+Support Bay+Observatory, Stargate, Citadel). Tech Level 3, of course, is everything else.
Map Control-Determines if you can expand, harass, attack, and defend. Determined by Technology, Attacking, and Unit Count. Judged by Low, Medium, and High. Low means you're in your base. Medium means you've split the map. High means you've contained them.
Example Situation: You have reached 140 supply in a TvP. Your +1 upgrade just finished. Do you...
A) Push out towards the Protoss 3rd
B) Push out and expand at your 3rd
C) Sit and do nothing in case of fast arbiters/Bulldog attack.
If you were to pick A, you would likely lose some Unit Count in exchange for map control. If you picked B, you would likely be able to increase your income and your map control slightly. If you do C, you will likely lose map control.
Now that we've gotten the ridiculous amount of Starcraft mechanics out of the way, it's time to start.
Situation #1
You are halfway done with your first Barracks and your scout has seen a 12hatch/11pool build. You are cross-distances (6 vs. 12) on Python. There is a scouting drone in your base. Zerg appears to be making primarily drones. Do you..
A) Throw down an expo at your nat.
B) Throw down a rax and a gas.
C) I've already thrown down a gas, and am about to build a factory.
D) Bunker Rush the noob.
Income: 8
Production: 1
Unit Count: 13/18
Tech Level: 1
Map Control: Low
Poll: What do you do?
(Vote): Throw down an expo at your nat.
(Vote): Throw down a rax and a gas.
(Vote): I've already thrown down a gas, and am about to build a factory.
(Vote): Bunker Rush the noob.
