## What is 5D chess?

5D Chess is an absolutely brilliant piece of software. I suppose it technically qualifies as a video game. It was released this July, I believe. It’s like chess, but with more axes. It's technically 4D chess as it only has 4 axes, I don't really know what the rationale was behind the software devs naming it "5D", but it's not. It's 4D.

## It sounds interesting. What is meant by 5D?

Imagine a regular chess board. You have two axes; the y-axis (the long way down the board) and the x-axis (left and right). Some pieces move only along any one of the axes at a time (the queen, the rook), some pieces move along both axes at once (the knight, the queen, the bishop), and pawns can only move along the y-axis, but capture by moving one space in both axes at a time.

Next, imagine that each move that you (and your opponent) made was saved as a snapshot of the board on a linear timeline; each “board” being saved in chronological order, a linear progression of every move that has been made, each one strung up so it appears immediately after the last. This is a third axis — which we will call the “t-axis” (t for Time) or “time axis” for the purpose of this post — which corresponds to the x-axis. I will explain axis correspondences, just not right now.

Now imagine if you could send a piece back to a previous board along the t-axis. You can’t alter the past on your current timeline; that would negate all the boards you have played since that point on the timeline. Therefore, a second chronological progression of boards (or, in simpler terms, a second timeline) is created, branching off from the initial timeline. The ‘present’ shifts backward to the new timeline, and you play moves on the altered timeline until the ‘present’ meets up with your initial timeline. Congratulations! You are now playing two simultaneous games of chess! We will call this timeline axis the “l-axis” (l for timeLine), which corresponds with the y-axis. Again, I will explain correspondences. Just hang on.

Keep in mind that we have two additional axes on top of the x-axis and the y-axis; we have the x,y,t, and l axes. Again, this technically makes it 4D chess, not 5D chess. I don’t know why the creators of the software titled it as 5D. The pieces do not move along a spatial z-axis.

## What do you mean when you say the t and l axes “correspond” to the x and y axes?

In traditional chess, you can only move pieces along the x-axis and the y-axis. In 5D-chess you can move pieces along the t-axis and the l-axis as well as the x-axis and y-axis. Again, this is four dimensions, but that’s beside the point.

The t-axis corresponds to the x-axis in that any piece that can move along the x-axis can move along the t-axis. This means knights, bishops, rooks, the king, and the queen. All of these are pieces that you can move backwards in time in order to create a new timeline.

The l-axis corresponds to the y-axis in that any piece that can move along the y-axis can move along the l-axis. This means knights, bishops, rooks, the king, the queen, and pawns. All of these are pieces that you can move between the the present timelines. Please note that moving between the present timelines is not the same as moving into the past; it’s a separate axis for reasons that I will explain later.

For example, pawns can only move forward on the current timeline (solely on the y-axis), or forward between the present timelines (on the l-axis), but cannot move forward onto a prior chronological point on the linear timeline (which is the t-axis, forbidden.)

## In traditional chess, the knight moves two spaces along the x or y axis and one in the other. How does this work between the t-axis and the l-axis?

Very astute! You’re a clever one for asking that question. In 5D chess, for all the pieces the movements are generalized as movements per axis. Movements per axis. This means that the knight moves two spaces along any one of the four axes, and one in any other of the four axes. This also applies to diagonals (queens and bishops), in which they move one in any of the four axes and one in another, or two in any axes and two in another, and so forth.

Taking the given example of the knight, if the knight is moving one chronological move back in time, he must move two spaces along the x or y axis in order to “complete” his movement of two in any axis and one in another, in this case he would move two in the x-axis or y-axis and one in the t-axis. If the knight moves two chronological moves through the t-axis, he need only move one space along the x or y axis in order to “complete” his movement of two in any axis and one in another. Likewise, if the knight moves three chronological moves through the t-axis, he “completes” his movement of two in any axis and one in another, and his position remains the same. This is also the case if he moves two chronological moves through the t-axis and once through the l-axis.

Let’s try another example. The rook can not move two axes at once, meaning that he cannot simultaneously move between the y-axis and the x-axis. This also means that he cannot simultaneously move between the t-axis and the l-axis. Remember, piece movements are quantified as movements per axis. He can only move through only one of the four axes at a time. Therefore, he can move along the x-axis on the same board, the y-axis on the same board, he can move along the t-axis and his position remains the same, or he can move along the l-axis and his position remains the same.

The same principle applies when taking the example of the bishop. With any given move, the bishop moves once along one axis and once along another. Taking this in terms of movements per axis, with correspondence in mind, if the bishop moves one space along the t-axis, it must move one space along the x-axis or the y-axis. If the bishop moves two spaces along the t-axis, it must move two spaces along the x-axis or y-axis. If the bishop moves one space along the t-axis and one space along the l-axis, it “completes” it’s movement-per-axis, and does not need to move along the x or y axes.

Let’s take one more example, just to really hammer in the nail. This one is the most complicated. In terms of diagonals, the queen moves much like the bishop; once along one axis and once along another. This means that when the queen moves once backwards along the t axis, the queen needs to move along the x or y axis. However, the queen can also move straight along the x or y axis. This means that if the queen moves two places backward chronologically along the t axis, it must move twice along the x or y axis, and so forth.

## Do I have to capture the king in every iteration of the l-axis (timeline) in order to win the game?

No, you do not. You simply have to capture the king in any one timeline in order to win the game. This means you must defend your king in the past as well as the future; you must think ahead and plan out every possible move along every possible axis. Or, you could fly by the seat of your pants and play around with it just for fun. I will admit that accidental victories have happened to me. Many times. It’s a lot of fun.

## Where can I get this piece of software?

It’s on Steam and Humble Bundle. You can investigate on their website, which I will link to here.