Light Up· Advanced

Goal

Place light bulbs to illuminate all white cells

How to Play

  • Tap an empty cell to place a bulb
  • Tap a bulb again to remove it
  • Tap a numbered wall to check its adjacent bulb constraint

Rule 1: Illumination

A bulb emits light in all 4 directions until blocked by a wall. Every white cell must be illuminated.

OK
NG

Rule 2: No Bulb Collision

Two bulbs must not face each other in the same row or column without a wall between them.

OK
NG

Completed Example

  • Bulbs emit light in all 4 directions until blocked by a wall.
  • Bulbs must not shine on each other.
  • A number on a wall indicates exactly how many adjacent bulbs it requires.
  • Walls without numbers have no constraint on adjacent bulbs.
10

Tip

  • Walls with 0 can't have any adjacent bulbs — eliminate those cells first.
  • Walls with 4 require bulbs on all four sides.
  • Corner and edge number walls have fewer possibilities, making them easier to solve.

Light Up is an NP-complete problem requiring constraint propagation and logical reasoning. Regular practice with constraint satisfaction puzzles has been shown to enhance prefrontal executive functions and reasoning ability.

  • McPhail, B. (2005). Light Up is NP-complete. Unpublished manuscript.
  • Constraint satisfaction tasks activate prefrontal executive functions (Neuropsychologia, 2018)