### Heisenberg Chess

- Where is the Piece?
- What Piece?!

After the "Physics and Chess" variants (from where Magnetic Chess was invented), Claude and I discussed the introduction of Quantum Mechanics into Chess in rec.games.abstract. Here is my proposal:

Heisenberg Chess

This variant was invented by Joćo Pedro Neto, in January 2000.

1. The FIDE rules apply except in the following:
2. Definitions:
1. Some moved piece A is seen by B, if that movement includes some square in the capturing range of B.
2. The distance 'd' between two squares is the maximum between the row and the column differences (egs, d(a1, b3) = 2, d(a1,b2) = 1, d(a1,a5) = 4)
3. By the Heisenberg Principle, every moving piece that is seen by any opponent piece, either change its speed or its position (player's choice):
1. Change of Speed: The piece start moving (from the square seen by some opponent piece) as if it was a different piece. The new movement is defined by the following order: Q moves as R, R as B, B as N, N as P. (note: for knights, the movement, is defined just by the immediate forward square from the original position. E.g., for Nb1-c3, it's square b2. For Nb1-d2, it's c1). E.g:

. . . . . . . .
. . . . p b . .
x . . . x . . .
n x . x . . . .
. . . . . . . .
. x R x B . . .
x . . . x . . .
. . . . . x . .

After moving north, Rc3 is seen by the opponent at c5, and changes its direction, start moving as a bishop. It can also take the black bishop.
2. Change of Position: If the piece is seen at square S by N opponent pieces, it changes its position to any empty square at distance N from S (except to those squares that he could move in FIDE chess). E.g.:

. . . . . . . .
. . . . . b . .
. . . . . . . .
n . x . x . . .
R . . . B . . .
x . N . x . . .
x . . . x . . .
x x x x x . . .

The squares marked by 'x' shows where the Knight can go (it may also capture Na5), if the player decides to change the position, by a Nb5 or Nd5 move. Why is this? Because the immediate forward square for those moves (square c4) is seen by two opponent pieces.