_Teaser_ is a puzzle game in a 3×3 grid of bits. Each bit can be either 1 or
0. The rules are simple. The player can change a 1 to a 0, but not the other
way around. When changing a 1 into a 0, it also influences its neighbours.
When performing the change in a corner, each adjacent number (including
diagonally) switches state. When doing the change in one of the four edge
positions, the entire edge changes state. Lastly, when doing the change in the
centre all adjacent (excluding diagonally) change state. The goal is to get
all ones, except for the centre.
