Black Box

Find the hidden balls by firing laser beams into the box. A beam hitting a ball head on is absorbed (H). A ball diagonally ahead deflects the beam away by 90 degrees. A beam returning to its entry, or deflected before entering, is reflected (R). Matching numbers identify a beam’s entry and exit; select either end to highlight both.

Place ball guesses inside the arena. Check guesses becomes available when your count fits the puzzle’s range. A wrong check highlights one contradicting beam (!) or reveals a new counterexample (+), without exposing the balls. Change a guess or make another move to check again.

Some layouts have multiple solutions. Any allowed number of balls with identical beam behavior wins. Locked cells (✓) cannot change until unlocked; edge locks toggle the whole row or column using the upstream majority rule.

Solve reveals the actual layout and does not count as a win. A crossed ball (×) is an incorrect guess; M marks a missing ball. Undo restores the previous state. Restart clears guesses, fired beams, locks and history for this puzzle.