Binairo Duo: Logic Puzzle

Binairo Duo is the classic two-colour logic puzzle - also known as
Takuzu, Binairo or Binary Sudoku - rebuilt for one thumb.

Every grid starts with a handful of amber and azure tiles. Tap an empty
square to cycle it: empty, amber, azure. Fill the whole board so that it
obeys three rules. Three tiles of the same colour may never touch,
across or down. Every row and every column holds exactly as many amber
as azure. And no two rows may be identical, nor any two columns.

That is the entire game. No timer to beat, no lives, no energy bar. Four
sizes run from a 4x4 warm-up you can finish in a lift to a 10x10 expert
grid that will hold you all evening.

Every puzzle is generated fresh and then checked by the very same solver
that powers the hints, so there is always exactly one answer and never a
reason to guess. Stuck? The hint button is free and unlimited: it circles
the next tile and names the rule that proves it, so you learn the trick
instead of being rescued.

A symbol mode adds a dot and a ring to the tiles for easier reading.