Not the author, but the grid is simultaneously a tape/program and a maze. At each step, two bits of the program are read and converted to a move of the blue box. Each set bit is also a wall in the maze which blocks movement. Note also the instructions at the bottom. I found the introduction simple enough (but maybe the game was updated since you asked).

Edit: Beat the game. Cool concept, I found the levels to be on the easy side though. Some ideas for if you wanted to extend it: You could have "stuck" bits, different kinds of boxes (different rules, or "doesn't die from hitting a wall"), and multiple boxes and/or goals.