Tango 8x8 grids

The Tango 8x8 puzzle

The 8x8 Tango grid marks the move to intermediate play. With two more rows, columns and suns/moons per line than the 6x6, it introduces longer deduction chains: the first cell no longer always resolves immediately, and you often have to combine several constraints before a symbol becomes certain.

The key technique here is forward counting by row and by column. On an 8x8 grid, every row and every column holds exactly four suns and four moons: as soon as a row reaches its quota for one of the two symbols, every remaining empty cell in it is automatically deduced to be the other. Combine that counting with the three-in-a-row rule and with the = and × clues, which propagate a known value to a still-empty neighboring cell, and grids that looked frozen unlock.

The 8x8 rewards discipline: track the sun and moon count row by row rather than holding it in memory, because across eight columns the eye gets lost fast. As always, the solution is unique and fully logical; you never need to guess.

It is the format most daily challenges use once the difficulty picks up: a fine balance between depth and solving time. Once comfortable, move up to the 10x10 for the expert size, or drop back to the 6x6 to race the clock. The 8x8 grids are unlimited and free.