Fill every square. Keep four things in balance.
Stuck? A hint explains one deduction and lets you apply it. Check marks current rule violations without giving away the solution.
Keyboard & helpful details
Use arrow keys to move, 0 or 1 to enter, and Backspace or Delete to erase. Ctrl/⌘ Z undoes; Ctrl/⌘ Shift Z redoes. Clues stay locked. Large digit buttons work on the selected square.
Difficulty considers deduction types, the number of dependent rounds, and how many moves are available at the start. All new puzzles have one solution and a verified logical solve.
The timer starts on your first entry and pauses while the page is hidden or a dialog is open. Turning it off only hides it. Progress and history save locally when browser storage is available.
To play offline, download this HTML file and open it in a browser. No installation or internet connection is needed.