Never three

放置光盤上的棋盤沒有在一條直線上具有三個。

Put as many discs on the checkerboard as you can. But beware: the centers of any three discs should not be on a straight line. Henry Dudeney and Sam Loyd first published a similar puzzle.

This puzzle app proposes first small sizes, which are easy to solve. They are a good introduction. Then you can challenge yourself with large checkerboards. You can find several solutions for each size. Try to find them all. You will train your logical and systematic thinking.

I designed this app for tablets. You can use it too on smartphones, but their screens are too small for longer play.