Strata5

Strata5 is a 1984 uncredited game, published at Milton Bradley.

The game is played on a 8x8 board with stackable pieces that are able to created complex 3D structures.

Each player initially has six color pieces with a red side and a black side. These pieces also are numbered, each player gets the set of labels {2,2,3,4,5,6}. There's also 32 building blocks with area 2x2, which connect to each other like Lego pieces.

The idea is to build structures by stacking the building blocks up to the height of five levels. The color pieces are able to move within the structure (the number label determine their moving range). The rules are more complex and intertwined including blocking, capturing, and piece flipping ludemes. You can read the original rules here. Another nice and illustrated explanation is found here.

The main problem with this game is the lack of interaction between the players. The board is too big. If one player tries to create a path to get near the opponent, to capture some pieces, this delay is fatal, and the opponent will win by stacking to level five. Some players suggest reducing the playing area to 7x7, which forces structures to interact, giving opportunity for captures.

There is a 2000-word report by Chris Lynd trying to fix the rules of the game. I don't know if this fix produces better gameplay, but it is not a good look for the original design process.