Fields of Action' was invented by the great Sid Sackson, who was inspired by Claude Souci's 'Lines Of Action'. The rules used here are taken from R. Wayne Schmittberger's 'New Rules For Classic Games'.
Pieces move, in any direction, a number of spaces equal to the number of adjacent pieces.
They may pass over pieces belonging to either player, but can land only land on an enemy piece, which is captured. An isolated piece may move any number of squares in any direction, provided that it does not make a capture and that it ends its move adjacent to at least two pieces. Moving a piece changes the available moves for itself, all the pieces adjacent before it moved, and all the pieces adjacent after it moved. This seems to make long-term positional strategy almost impossible. You should extract from the downloaded zip file preserving path names.