I like how you took simple runes and made a puzzle out of combining them in different ways. Some of the shapes are rather complex, and it's surprising how they can be broken down into the same simple pieces.
I could see this being expanded with even more shapes, but you may want to provide some sort of log for the shapes the player has made already so they don't forget. With just the ones here, I was starting to forget them after a while. Having this sort of log would allow you to add more things without overloading the player with possibilities :)