Found an interesting, repeatable bug that can be invoked when you first start a mining game (at least when you reach a level that unlocks playing speed 35/100). If you move the slider to 0 and then to the max allowed speed based on your level, the puzzle floor moves up dramatically faster (hard to handle without items, I gotta say). It's kind of a situation-specific bug that doubles as a challenge mode.
Btw, I've been messing with the turbo speed "feature" just for fun, and at the risk of "spoilers" I was wondering exactly how fast the blocks move upward at certain levels. To be very non-specific, is the rate supposed to be 15-25 seconds per line at difficulty 0 and more like 10-20 seconds at difficulty 38-ish? Looks like in the middle of my testing, I've "unlocked" two turbo modes. The first one, if it's really a turbo mode, raises lines of blocks at about 6 seconds/line (woohoo, I can handle it without tools!). The second one, which pops up less often, "raises the roof" at a rate of about 1-2 seconds per line...and I'm pretty sure that one's gotta be too fast for pretty much all players at this point, since they'd have to make a normal match every half-second or so just to stay alive. =)