Is it possible to Up and Down at the same time, and have it register on BYOND? For example, for combos for a fighting game close to Street Fighter?
Nah, BYOND has key quoing (Spelling is wrong,) basically that means that you can only press one at a time before they stack up. But maybe this post by Garthor can help you. [link]
ITG do you mean like this demo Combo System by Rifthaven.

->Calus CoRPS<-