Akari is a binary determination puzzle where all cells are lit-up by placing lightbulbs and no lightbulbs shine on each other.
The objective is to light up all white cells, subject to the following rules:
- Lightbulbs shine every cell vertically and horizontally until they reach a black cell or the boundary.
- Numbers in some black cells denote the number of lightbulbs in adjacent cells.
- Lightbulbs themselves are not lit by other lightbulbs.
A standard 10x10 akari and its solution.
Unless otherwise indicated, standard akari rules apply to all variants.
Coloured Akari: Coloured lightbulbs are used to lit-up the grid. Light from bulbs of the same colour cannot cross and cells are coloured depending on the colour of lightbuls in adjacent cells.
Regional Akari: The grid is divided into regions. There must be exactly one lighbulb placed in each region.
Queens: In addition to shining horizontally and vertically, lightbulbs shine diagonally as well. Clue numbers now count lighbulbs placed in diagonally adjacent cells.
Ex: Clues are split into two colours, one colour counting bulbs in adjacent cells as standard, the other counting lightbulbs that shine light directly upon the wall.
Mirror: Some cells have either a diagonal split or a triangular block. Light hitting the mirror reflects off at 90°. These cells otherwise act as a black cell in that they do not need to be illuminated and no lightbulbs can be placed in one of these cells.
Twin: As standard except that lightbulbs now shine upon exactly one other lightbulb.