◆　Rules

White-Black Pearls is played on a rectangular grid of squares, some of which contain circles; each circle is either "white" (empty) or "black" (filled). 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; all turns are therefore 90 degrees.

The two varieties of circle have differing requirements for how the loop must pass through them:

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

◆　20 problems for beginners
　　　（Size of a cell 6x6 20problems）

◆　50problems 　
　　　（Size of a cell 10x10 10problems,18x10 20problems,24x14 12problems,36x20 8problems）