Masyu

Masyu is played on a grid of squares. Some cells contain white or black circles. The goal is to draw a single continuous non-intersecting loop that properly passes through all circled cells. The loop must enter each cell it passes through from the center of one of its four sides and exit from a different side.

1. White circles must be traveled straight through, but the loop must turn in the previous and/or next cell in its path.
2. Black circles must be turned upon, but the loop must travel straight through the next and previous cells in its path.