Black Box
What do H and R mean in Black Box?
H means the beam hits a hidden ball head-on and is absorbed. R means the beam is reflected back to its entry. A ball just beside an entrance can reflect the beam before it enters; R does not identify a ball directly in front.
Worked example
A numbered entrance and exit form a matching pair for one shot. They describe the same path, not two separate hidden balls.
What to check on your board
Apply the rule above to your current board, then verify the remaining puzzle constraints. The example explains a local deduction; it is not a solution to every randomly generated board.
Checking your next move
Keep a note of each shot’s entry and result before testing another arrangement. For numbered results, pair the matching entrance and exit instead of counting two independent clues. When a hypothesis fits one shot, replay the other recorded shots against it before accepting the ball positions.
Using this reference
For Black Box, read the rule and the worked example together before opening the game. Separate what the rule explicitly requires from what only seems likely on the current board. A useful next move is one you can explain from the visible constraints, not merely a pattern that looks familiar.
If you get stuck, isolate a smaller part of the position and list what is still possible there. After a move, check the affected rows, regions or connections again. The reference explains the documented rules; progress, controls and save behavior belong to the linked game.
Read the developer’s manual ↗ · Open the developer’s browser version ↗
Manual inspected: · Simon Tatham & contributors · MIT