A closer look at Lantern Grid
One bulb sends four straight beams
A bulb lights its own white cell and white cells in the same uninterrupted row and column. Walls and grid edges stop the beam. Light cannot turn a corner. Two beams may cross or overlap on empty cells; two bulbs may not see each other along a clear line.
Numbers count bulbs, not bright cells
A number on a dark wall gives the exact count of bulbs in side-adjacent white cells. Diagonal bulbs do not count. A zero forbids bulbs beside it, but those cells still need to be lit from somewhere else. Numbered walls block light just like other walls.
Edit, inspect and explicitly check
Wrong placements are allowed so you can compare outcomes. Toggles counts every added or removed bulb. Check lighting adds no toggle and tests dark cells, mismatched wall counts and visible bulb pairs. All three counts must be zero. Only a successful check locks the board. Undo reverses one toggle, including after a win. Retry clears the attempt on unchanged clues.
A small checked collection
New puzzle cycles five original prepared boards, then repeats, clearing the practice address. Load beginner board restores the first lesson’s exact clues at zero toggles. Refreshing that practice address restores the clues without saving bulbs or history. The board is untimed and needs no account, payment or ad action.
Keyboard and accessible state
Tab reaches white cells and controls. Enter or Space adds or removes a bulb. Arrow keys move to the next white cell in that direction, skipping walls without wrapping. A solid dot marks a bulb, a plus marks an illuminated empty cell and a middle dot marks a dark empty cell. Labels and pressed states describe the same facts without relying on colour. Common rules follow Nikoli’s Akari; the numbers, code and explanations are original, with no affiliation claim.
Common questions
Can two empty cells share the same light beam?
Yes. An empty cell may be illuminated by several bulbs. The forbidden case is a bulb directly illuminating another bulb along a wall-free row or column.
Does every white cell need its own bulb?
No. Most white cells receive light from another bulb. A bulb illuminates itself too.
Are wall numbers satisfied when their neighbours are all lit?
No. A number counts adjacent bulbs, not the number of lit neighbours. All numbers being exact still does not guarantee every white cell is lit.
Is a low bulb or toggle count the goal?
No minimum count is required. A win requires full illumination, exact numbered-wall counts and no visible bulb pair. No health or measured ability benefit is promised.