*In this maze, each of the large squares represents a two-dimensional
slice of the maze. You are the blue square; you can move on white squares,
but not red ones. You move by either clicking on a small square that is
in the same large square and shares a side with your present square, or
by clicking on a small square that is in the same position as your present
square, on a large square that shares a side with your present large square.
If you aren't sure if a move is legal, try it. If you're allowed to move on a
square from your present square, the computer will let you; if you can't make
that move, nothing bad will happen — you just won't move anywhere. The goal
is to get to the light green square.*

The maze is a hypercube; in the same sense that a diagram might represent a three dimensional structure by showing some two dimensional slices one above the other, this maze represents a four dimensional structure by a grid of two dimensional slices.

In eighth grade, when I first wrote this, I was very interested in higher dimensions, and I tried to learn to visualize in four dimensions; I never really succeeded, but I did learn to visualize the shifting three dimensional cross sections of hypercubes passing through three-space at a couple of different angles. Visualizing higher-dimensional objects is hard (impossible, by some sources), but doing math or programming in higher dimensions is not by nature more difficult than doing things in two dimemsions.

Does the maze look flat? Is it really four-dimensional? Let me ask you
a question. What can you see that doesn't look flat? All the images you see
are two-dimensional. A movie or a 3D game doesn't look flat because it
*represents* a three-dimensional area in a two-dimensional way, and you
learned as a child to perceive that as three dimensional. This maze also
*represents* a four dimensional maze, just like a flat schematic diagram
represents something three-dimensional. The picture on your screen is two
dimensional, just like every other picture on the web, but the maze that's
represented is four-dimensional.

An Author's Musing Memoirs About his Work: Retrospective Reflections, Retracings, and Retractions