That was a good game — it felt like the sort of thing Nitrome puts out in terms of polish and fun. The mechanics are well thought through and the money-as-move-counter adds a nice layer of complexity/replayibility to each level, without feeling like a chore.
Having now gotten gold on all the levels (76 was the last to fall), I think there's probably room to further consolidate them. For instance, there were a handful of levels that seemed to have unintended solutions where you can finish with a higher number of coins than the gold-medal number. Equally, the mechanics don't seem to yield 80-levels-worth of discrete ideas, which leads to a sense of repetition as you get deeper in. With that said, nobody ever went out of business making web games with lots of levels :)
One small technical point: I'd consider having a keyboard button to switch between block and hammer, as the mousewheel isn't really viable for trackpad users, and involves two finger scrolling ad nauseam in the hope that it will land on the tool you want to use.