A jugar! is Spanish for "Let's play" -- a idiomatic way to say "Let's [verb]!" in Spanish is to place "a" in front of the infinitive (ending in ar, er, or ir) form of a verb.
No mas is "no mas" -- No more, so to speak. As for Steaver's Impossible Room, I think I remember an MSN conversation a while back (years ago) where Steaver asked something about refining and remaking a level of mine in Cheapo... and looking back at it, I suppose that was it. Steaver always had a strange problem with giving other people credit for levels, if I remember right. Although that thread seems to be more proof of the "drop the lemming through the one pixel floor in Cheapo" glitch. I remember showing him the level, and he went and made almost the exact same level for the Cheap Challenge.
Anyways, I see where the 100% in Undermined comes from -- my solution doesn't allow any miners to stop themselves, so a few of them go through the brick and die. Thanks to Conway and JM for their response.
80% on Razor's Edge 3 seerms even less feasible... I know you can do it with 6 builders... but not 5 though. Maybe something could be done with my solution to refine it? I don't know.