Light Up (Akari)

Medium Light Up uses a 7×7 grid with about 25% wall density and 60% of walls numbered. The larger grid creates longer corridors where light rays extend further, making visibility conflicts more impactful.

Corner and edge wall deductions become important here. A numbered wall on an edge has only 3 possible neighbors, which tightens its constraint. You will also start needing light-ray exclusion: if placing a bulb somewhere would conflict with an existing bulb visible down a corridor, mark that cell.

The dark-cell toggle becomes useful at this size. Enable it to spot unlit regions that need attention. Ready for more? Try hard (10×10).