There are a handful of "generic BOs" that you can apply to mapgen maps. Sometimes you want a normal build, sometimes you want to spam pgens because there's lots of reclaim, sometimes you want to rush a transport. You can learn these builds by learning specific builds for ladder maps, e.g. a transport rush map will teach you the transport rush generic BO. Obviously a "refined" BO would be better than a generic one that you slap together. But there's got to be less than 10 total "generic" BOs that I would draw on:
- Standard fac 2pgen 2mex
- Hydro build fac 4 mex 1 hydro
- near hydro build fac 1-2 pgens 4mex hydro + more mexes before hydro finishes
- first bomber 1 pgen 1 air fac 1 pgen assist fac
- second or third bomber (almost the same thing but make 1-2 engies first)
- first jester 2 pgens air fac
- spam power for transport rush (and/or make inties first to shoot down enemy trans)
- spam power because there's lots of reclaim like on Daroza's
- factory + 1-2 mex + walk ACU, let engies build the pgens, because you need ACU to hoof it, this can be good when there are very few mexes at home and you want to expand ASAP
- spam factories for big tree reclaim early, so you build less power than normal, you'll build the pgens up later
A lot of these are so similar to each other maybe it's silly to count them as separate builds so maybe this is more like 5-6 builds than 10. If you know these 10 generic builds I think you can pick a decent build for 99% of the mapgen maps you might get. It's enough that you probably won't fall behind early against a player of similar skill.
