I did the ones with the trees by the windmill. The last tree is the one I had to just try all the options on because I was getting frustrated not seeing anything on the branches. (Blacked out for Link, but I'm sure he'll get it right away.) If you do get that last tree on your own, let me know why the solution is what it is. Energy, if you know, maybe post it up for me and black it out. Thanks!
I'll explain the trees. As you learned from the earlier panels the tree diagram on the panel matches the layout of the tree in front of the panel. And the solution matches the apple location. On the panel before the last panel, you noticed that the branches of the tree in front of the panel didn't quite match up to the diagram. You had to look at that tree from the other side to get it to match the diagram.
Last tree panel however the tree doesn't match the panel at all, even if you look at it from a different direction. And there is no apple on the tree to show the solution! Well if you compare the diagram and the tree, there is exactly one fewer branches on the tree than the panel. And it appears like where there would be a branch it has broken off. The apple was on that branch and removed from the tree. For another hint, I think you can see the broken branch lying on a table on the other side of the gate the panel opens. And when you open the gate the apple is sliced and lying near the branch.
I also got stuck in the marshy area with the panels opposite each other. There are "l" and "---" shapes, and you need to surround them, but I can't because you can't overlap your line.
Yes, you need to surround them. But that one symbol in the middle is impossible to surround... If only it was next to an edge of the panel like those other two symbols...
I also couldn't get the panel with the triangle in it on the ground at the starting castle.
You'll see more of them strewn about the world. If you find another and succeed at solving, try to figure out why that is the solution and then test your hypothesis by going back to one you haven't solved. That's a lot about what this game is about. Discovering a solution and then determining why it is a solution until you understand the mechanic.
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The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time.