A <a href="https://en.wikipedia.org/wiki/Connect_Four" class="extiw" title="w:Connect Four">Connect Four</a> board with the colors split along the diagonal, giving 18 lines of four for each side.
<a href="//commons.wikimedia.org/wiki/User:Ilmari_Karonen" title="User:Ilmari Karonen">Ilmari Karonen</a>
<span class="int-own-work" lang="en">Own work</span>