Chalk Bead Rows

A quiet chalkboard puzzle built on three simple rules and a lot of clean deduction. Every slate is a square grid, and every cell takes one of two chalk beads: a hollow ring or a hatched bead. Tap a cell to cycle it from empty, to hollow, to hatched, and back again. Coral beads are already chalked on the slate and stay locked. THE THREE RULES 1. Half and half. Every row and every column holds exactly as many hollow beads as hatched beads. Three of each on a 6 x 6, six of each on a 12 x 12. 2. Never three alike. Three identical beads may never sit side by side, across or down. A run of three pulses on the board the moment it appears. 3. No two lines alike. No row may repeat another row, and no column may repeat another column. When two finished lines match, both are underlined in coral. This puzzle is known as Binairo, Takuzu or the binary puzzle. There is no arithmetic and nothing to guess: every slate has exactly one valid arrangement, and it can always be reached by reasoning alone. FOUR SLATE SIZES - 6 x 6 for a two minute sketch - 8 x 8 where run blocking chains start to matter - 10 x 10 where line uniqueness begins to bite - 12 x 12, the full classroom board EVERY SLATE IS FRESHLY CARVED Boards are generated on your device, then checked by a solver to confirm that exactly one arrangement of beads satisfies all three rules. You will not be handed an ambiguous board, and you will never be forced into a coin flip. TOOLS IN THE CHALK BOX - Undo steps back through every bead you placed. - Hint corrects a bead that contradicts the answer, or chalks in one the rules already force. - Assist shades any line whose count of one bead is already full, so the rest of that line is settled. - Wipe chalk clears your work and keeps the printed beads. - A timer runs quietly, and your best time is kept for each slate size. RECORD AND CHALK MARKS Slates finished, hint-free finishes, your longest hint-free run, minutes spent and a best time per size are all logged. Thirteen chalk marks are there to collect, from your first finished board to an hour of total solving. MADE TO BE CALM - Completely offline. The app has no internet access at all. - No advertisements of any kind. - No sound. Ever. Feedback is visual, with an optional short haptic tap. - No accounts, no sign in, no tracking, no analytics. - Everything you do stays on your device. - Portrait only, drawn entirely in chalk on a slate green board. Suitable for everyone. There is no money, no wagering, no violence and nothing frightening here. Just chalk, beads and three rules that fit on one line each.