Maze generator in Mathematica.

maze

MazeGraphics[m_, n_] := 
  Block[{$RecursionLimit = Infinity, 
    unvisited = Tuples[Range /@ {m, n}], maze}, 
   maze = Graphics[{Line[{{#, # - {0, 1}}, {#, # - {1, 0}}}] & /@ 
       unvisited, 
      Line[{{0, n}, {0, 0}, {m, 0}}]}]; {unvisited = 
       DeleteCases[unvisited, #];
      Do[If[MemberQ[unvisited, neighbor], 
        maze = DeleteCases[
          maze, {#, 
            neighbor - {1, 1}} | {neighbor, # - {1, 1}}, {5}]; #0@
         neighbor], {neighbor, 
        RandomSample@{# + {0, 1}, # - {0, 1}, # + {1, 0}, # - {1, 
            0}}}]} &@RandomChoice@unvisited; maze];
maze = MazeGraphics[21, 13]