You just have to play it over and over until you get a Dark Hypercube within the first 10 moves. Turn the gems with highest number into Hypercubes and if your lucky use the Hypercubes on flame / star gems. I was able to get 200k + and with the 30 moves pushed me over 3 stars. You just have to grind it out.

"Dark Hypercube: Match 6 or more gems in a row.
- When you swap a Dark Hypercube, it changes all of the gems of the swapped color to Hypercubes."