How are the mazes made?

Each maze is carved with the recursive backtracker algorithm: start in a corner, pick a random direction to an unvisited cell, knock down the wall, and back up when stuck. The result is a perfect maze: there is always exactly one path between any two points. The "watch it being built" button replays that carving. The hint button uses BFS (breadth-first search) to find the shortest way to the exit. The maze code is its random seed; the same code always produces the same maze.