## The Rules of Upright 3D Chess

The standard rules of 3D Chess apply, but the Knights and Pawns must be defined here.

### Pawns

Pawns may only move straight forward on the same level; when they capture, they may stay on the same level, rise, or descend. For example, a White Pawn at 4e4 may capture on 4d5, 4f5, 5d5, 3d5, 3f5, or 5f5.

### Knights

The Knight makes its normal move, or goes one square up or one square down from its normal destinations.

From 4e4, a Knight can go to 24 different places: 3d6, 4d6, 5d6; 3f6, 4f6, 5f6; and so on.

Notice that the Knight has a fairly flat profile and cannot make a "vertical Knight" move: it is illegal for the Knight to move from 1g1 to 3g3.

## Pawn Power In Chess

In two-dimensional Chess, each square of the board can potentially be attacked by at most two Pawns, so that every time you advance a Pawn you need to think carefully about the squares for which you have weakened your potential for Pawn control.

In Upright 3D Chess, each square is potentially attacked by as many as 6 Pawns, and therefore Pawn weaknesses are not quite as pressing. After, for example, 1. 4e4 N4g8-4f6 2. 4e4-4e5 N4f6-4d7 3. 4e5-4e6? Black can capture any of 5 ways, and though the Pawn at 4e7 is a bit blocked there are other e-Pawns that can be moved to get the pieces developed, and of course Black still can attack 4e5 with a Pawn -- in fact, with any of 4 Pawns.

However, Pawns still have very limited mobility, which was designed so that Pawn chains can still be formed and play their normal part in setting up walls that make the strategic terrain more interesting. The weaknesses on both sides normally caused by a Pawn chain will sometimes be absent.

For example, after 1. 4e4 4e6 2. 4d4 4d5 3. 4e5 4c5 4. 4c3 4c4, we have a perfect 2D Pawn chain. Black's 4th move here is probably wrong, but is played to set up the example.

Moving into the third dimension, 5. 5d4 defends 4e5 with a second Pawn, and reveals that a 3D Pawn "chain" is shaped like a a vertical wall.

## Remarks

The rules for this version of 3D Chess accept the negative of having 6 Pawn captures in order to achieve verticality. With these rules, pieces always move to the same squares as in 2D Chess (except for the Rook moving straight up and down). Pawns always capture onto the same color, and Knights always change color. Only the vertical component of the move is different than in 3D Chess.

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