Hi, I've posted how I did this game here. I didn't use double layer but by this method, the questions were still really easy.
https://7sage.com/discussion/#/discussion/8642/pt68-section-4-game-4-alternative-approach
For me it depends, but usually I think for 'X must be here' rule, I draw it since it's more easy to spot on and doesn't take much time. For 'X cannot be here', it the remaining variables are two or three, I think I prefer to draw them.
... this. I think the term variables was a bit vague. In ... />
By two sets of variables what I meant was even ... them as two sets of variables based on whether they they ...