Light Up

Light Up is played on a rectangular (usually square) grid consisting of white and black cells. White ones are conventionally “empty”, and black ones are “filled”.

The player operates with special marks - “lamps”, which can be placed on any white cells. Each lamp, once installed, creates four light beams: up, down, left and right. These rays reach the very boundaries of the field if there are no black cells on their way.

The player’s task is to illuminate the entire playing field in such a way that the lamps do not shine on each other. In this case, the intersection of light rays is allowed.

Game rules

In Light Up, some of the black cells contain numbers - from 0 to 4, and the other part remains without numbering. The number on the cell indicates the number of lamps that should be installed next to it (vertically and horizontally only, but not diagonally). During the game you must also adhere to the following rules:

• Lamps cannot shine on each other (must not be located in the same line or column without barriers between them).
• The light from each lamp spreads to all cells vertically and horizontally from it, and is intercepted only by black cells and the boundaries of the playing field.
• At the end of the game, all white cells must be illuminated.

If there is no number on the black cell, it is not known in advance how many lamps are next to it (and whether they are there at all). In the case of the number 4 inscribed in a black cell, the task, on the contrary, is extremely simplified - you need to install a lamp at each of its faces.

How to solve the puzzle

To win at Light Up, you must use logic and deduction, or rather, use the method of elimination to prevent all obviously false moves. In the form of specific tips and tricks, this can be expressed as follows:

• Always start the game from the black cells with the highest numbers (3 and 4), and from the black cells that are located near the boundaries of the playing field.
• Mark the cells where the lamp most likely will not be placed.
• If a lamp placed diagonally to the number 3 blocks the two cells surrounding it, this will make it impossible to place three lamps around the number. Accordingly, diagonal cells around the number 3 can never have glowing elements and can always be marked with crosses.
• Two numbers 3, between which there is an empty cell, imply the installation of a lamp in it.
• If number 1 is adjacent diagonally to number 2, and one of the cells next to number 2 (not adjacent to number 1) is empty or fenced off by a wall, then no more than one lamp can be placed in two cells common to two numbers . This means the last lamp must be in the remaining cell around the number 2.

In text form, the last 3 points may look complicated and unclear, but they can be easily understood intuitively as the game progresses. You will automatically exclude incorrect moves, and place lamps only where there is no alternative to their location!