chess

Chess player John Bartholomew plays opponents rated below 1000 on Chess.com and comments on optimal strategy and typical mistakes at that level. It is part of his Climbing the Rating Ladder series.

Mathologer shows a simple idea, the commutator, that lets anyone who can solve the first layer design their own full Rubik's cube solution. The same idea carries over to other symmetric twisty puzzles such as the Megaminx.