Echelon is a three-dimensional abstract strategy game in which two players build a structure while attempting to get five cubes of their own color in a row. Starting with a black "starting cube", players alternate placing in one of two ways: 1) Playing three cubes in a row (as viewed from above), with at least one cube on top of a preexisting one, or; 2) Playing two cubes as above, but also removing an edge-adjacent cube from the structure. The game also includes two "anchor cubes" of each color, which may not be removed from play by either player, as well as one "shift cube" for each, which may only be removed by the owning player. Note: the front of the package claims the game is suitable for 2-4 players, but the interior of the rulebook reveals that doing so entails purchasing another set of cubes (they were apparently sold in two sets; one with red and blue cubes, and the other with green and purple).