StarCraft2: MULE – can he work on one mineral patch with another SCV in parallel

It sounds like you're building a large army and using it to gain map control, but then are falling prey to things like drops and backdooring.

If you have map control your first thought should never be: Crush my opponent, as you're essentially sacrificing an advantage (map control) for an unsure victory (because he doesn't control the map doesn't mean he can't take you). Instead your thought should be: take the map. I think you'll find this change in philosophy will lead to situations where you have a much more powerful economy than him and you're able to kill him with attrition.

Now if you're falling prey to things like BD here is a quick check list for you:

• Are you scouting? an Observer should be the first thing you build out of Robo. If you don't go Robo, a Hallucination works just as well. Sometimes scouting means sacrificing some Zealots in a pointless charge to just get inside his base.
• If you're scouting, are you seeing it coming? Overlords on the edge of your base, Starport with Reactor + 3 Rax, all of these are indicative of certain strategies you should watch out for.
• If you see it coming, how are you responding? If you have map control that means you should be able to respond quickly. Shutting down these back door attempts is often a bigger victory than a straight up conflict
• Finally, Do you have map control? If you don't have map control that means he does, and if he's beating you with map control then your problem is not "how do I deal with a base trade?" but rather, how do I regain the advantage.

I've beat Terran with Protoss using photon rush.

1. Build probes constantly, 1st build probe will go to opponent, all others - go to minerals; 10-12 actually should be enough.
2. Build the 1st pylon outside of the opponent's start location - if you build it in the opponent base (after the choke) he will attack the pylon with large amount of SCVs. The Pylon should be built as close to the opponent base as possible.
3. Build 1 forge.
4. Build 2 cannons close to the opponent base - they will shoot up the ramp soon.
5. When these cannons are almost complete, send a probe to the opponent's base and build 1 cannon (you 1st pylon should give enough space for 1-2 cannons).
6. Opponent will try to attack your building cannon, but your first 2 cannons should be able to protect them. Keep you probe from being killed by SCVs/marines.
7. Build new pylon close to new cannon, once the new pylon is done, build 1-2 additional cannons not to far away from the 3rd cannon; it should be able to protect the new building. The new cannons should also be able to attack the command center.

After the last cannons been build they will start shooting the command center. The AI will give up quickly.

I did the above and finished sometime around 4:30.