I really came to appreciate how exploration of the map was a product of knowledge inside the players head. Understanding the rules governing puzzles using a given symbol opened areas of the map gated behind this symbol.
That's *cool*. The doors aren't a level gate, they aren't guarded by an enemy. The player progresses simply by knowing a rule that enables them to manipulate the gating puzzles.
This is very elegant. I'll be on the lookout for similar games in the future. #gamedesign