FillField Free

FillField is a quite difficult puzzle game with extremely simple rules.

The complexity of this puzzle is determined not by the complexity of the rules, but by complexity of the task. Rules are trivial: there is a rectangular box filled with dual-position switches. When you change the state of one switch, this leads to a change in the status of some (what exactly -- depends on the settings of the game) nearby switches. Goal of the game is to set all switches on the box in same position.

Full version can be get here: https://play.google.com/store/apps/details?id=org.asciigames.fillfield