In February 2002, Nicholas and Eric invented Blindfold Lego Maze.
I built a maze (shown) with enough room for a finger to fit in the pathway. Nicholas put on a blindfold without seeing the maze. I put Nicholas' finger where the maze starts (lower right in the above maze) and he tries to solve the maze by feeling his way to the exit (upper left) with just one finger.
I'm sure others have before or since discovered this fun game independently, but I couldn't find any references at the time.