The goal changed after the Owner played the first pilot: mine every tile, not dig to a chest. The quarry is now seen from above, with open ground along the bottom where the imps walk in.
Each imp marches in from its lane's spot (lane 1 from the left, lane 2 from the middle, lane 3 from the right) to the nearest tile of its color it can reach, swings its pickaxe three times, and the tile cracks, breaks into gems and goes into the imp's sack. Imps from different taps work at the same time, and waiting imps walk out from their slots when their color opens up.
Placeholder imps drawn in code: little horned, grinning miners with pickaxes, each with its color's symbol on its belly.
The lanes now hold exactly one imp per tile, so the only way to lose is to jam the 5 slots. 12 new levels, from three tutorials to an Expert finale, all proven winnable by the solver.
TREASURE!
