4x4 (aka Vier mal Vier) is an abstract 4-in-a-row variant in which 2 players use 16 grooved cubes to erect a wall between them, aiming to be the first one to create a sequence of 4 identical shapes in their own side of a wall, or of all 4 different ones. This row can be horizontally, vertically, or diagonally. The cubical building bricks are all unique, come in 4 colours, and the only placement restriction is that each colour is only allowed once in each level or column. When the last brick is added, the completed wall will be 4x4. On 2 opposing faces of each cube, a groove has been carved out. There are 4 distinct grooves, and the twist is that these grooves rarely mirror each other on either side of a cube. Therefor the wall face will look completely different to each player. The grooves are paired in such a way that within each group of 4 identically coloured cubes, only one cube has an identical shape on both sides (a different one for each colour). The other combinations are unique for that colour, and each combo occurs only one other time within the entire set. At the start of the game, the cubes are placed on coloured supply strips which show the 4 'footprints' of all the blocks that exist for each colour. The wall is build on the table surface between the players. Players can only see the top cube of each column and the shape of the groove on their side of the wall of the cubes below it. Forward planning, memory skills and deduction all come into play to some extent, as players above all need to prevent that the opponent gets the sequence of 4 first. The supply strips serve as gentle reminders of what is out there. The pro-version introduces the rule that an opponent can force a player to take back the last played cube if it would prevent the wall from completion, and instead insist on the placement of a cube that would result in a wall with the maximum amount of bricks. It also suggest the removal of the reminder strips.