Didn't? Pah. Hadn't yet. I said it was coming soon... At any rate, it's there now, and reading your solution after the fact I see I took a different approach to the oasis than you did. Of course, yours is perfectly valid as well. The '3' was only there for symmetry - I don't use it in my solution, but it's educational to see how you've used it.
As it happens, I explain the whole "checkerboard" thing in my solution, so if anyone was confused by that part, check out my write-up. But do go back to ralphmerridew's after mine, as e demonstrates a useful technique that I didn't. - ZM
Re: Solution to the sample
As it happens, I explain the whole "checkerboard" thing in my solution, so if anyone was confused by that part, check out my write-up. But do go back to ralphmerridew's after mine, as e demonstrates a useful technique that I didn't. - ZM