Copyright (c) 1975 Otto Maier Verlag Ravensburg
The game is played on an empty 5x5 square board.
OFF-BOARD - Each player has 9 stones in reserve
1st TURN - Each player places a stone on an empty cell.
TURN - On each other turn, each player must make the following moves:
First, he must slide one stone in any direction (no jumping allowed) moving at least two cells (so, it cannot move to adjacent cells).
Second, drops a stone from the reserve into the last empty cell moved over the first stone.
If the reserve is empty, pick another stone on the board (but not the moved one) and drop it on that cell.
EQUALIZER - On the second turn (the first turn where stones are moved), the second player may skip the first part of the turn (i.e., he may just drop one stone from reserve).
A player wins by making a (diagonal or orthogonal) 4 in a row, or
A player wins by blocking the adversary (i.e., leave him with no valid moves).
Some initial moves
2.b2b5 (drop a stone at b4) b3 (skipped move),
3.b5e5 (drop at d5) b3d1 (drop at c2)
A variant created by Michael Howe at 1994, called EPSILON, uses the same concept, but to align 5 in-a-row in a 7x7 square board, and with further rules to equalize game play. On the initial turn, the first play is forbidden to drop at the central square, and the second player must drop two stones on any two empty cells. Then, each player makes two moves (where each move has two parts, as in DELTA) with the restrictions (a) the dropped stone on the first move cannot slide on the second move; and (b) both stones on the first move cannot be used to pick and drop (after the reserve is empty) on the second move.
Check ETEROSCACCO for more information (in Italian...) on both games.