[MrQuincle]

Would be nice if there was also an "advanced" mode. Only highlight pieces that have less defenders than attackers. And highlight pins.

And I assume even more advanced modes highlight perhaps central squares that might be obtained and which open lines. See https://en.m.wikibooks.org/wiki/Chess_Strategy/Open_lines for a nice example.

[_ology]

Hm. If I were an advanced player I might be up to creating an advanced mode! ;-)