Very similar to mine. I've yet to try it in Extreme, but I imagine it'd tear up, considering how well it was doing on normal and hard. Although mine has more backtracking. Or possibly an equal amount, upon closer inspection.
The key for me is to put anything less than perfect gems around (but not in) the + intersection in the middle of your maze , whilst trying to build up for good combos. Then, once you've fully upgraded your gems, and are at about level 15/20, delete the rocks in the + intersection and plonk your gems down there, ensuring that you only choose gems you can eventually combine effectively (as well as lots of perfect amethysts - which need to be in the center of the + intersection). Always opt for a perfect opal if you see one come up, too (and unless I've already got a perfect opal in the area, I tend to dislike the perfect opal combo gem - the dmg aura one, as it's less effectively than an opal, tho it certainly stacks well with one... since opals don't stack).
Now, let's see if I can remember how to build it. All that sun-baking and clubbing has left me brain a bit numb.