[sduff]

Mental chess is a bit tough of a challenge. Why not try mental four in a row? Still a bit of memory work required, but not to the extent that chess or blindfolded go require.

I wrote an app to let you play, starting with playing with one colour, before moving on to invisible.

https://simonduff.net/invisilink to play in your browser, and a link to the Android app. Appreciate any feedback :)