Maybe switch the colours at the right from place, e.g. to "yellow-white-black-red" (from top to bottom)? This way you have to think before moving them. This is only a suggestion so I'll kept it on "grey (unevaluated)", till you've posted a reaction.
Maybe switch the colours at the right from place, e.g. to "yellow-white-black-red" (from top to bottom)? This way you have to think before moving them. This is only a suggestion so I'll kept it on "grey (unevaluated)", till you've posted a reaction.