(!potential spoilers for people who haven't played) In the Witness, how do I solve this puzzle? [duplicate]
I know this isn't the answer you're looking for, but I'd recommend coming back to this later. There are other environmental puzzles in other parts of the island that, once you have found them, the answer to this one will be obvious.
Really. I'd encourage you to stop reading now. The game is more fun the more puzzles you solve on your own.
But if you insist, here's my gingerly worded hint.
It looks like a piece of the circle is missing. Can you find a way to fill it in?