[TOMT][Reddit post] A technique for motivation using index cards, a marker, and 7 weeks

I've been looking for this comment for a while. It was a system dividing an index card into 49 boxes for as many days, and then marking each one with a "big fat marker" when you completed your goal that day. When you finished a month, then you'd do something special.

I'm pretty sure there was even a subreddit and and Android app dedicated to this technique, but I forget what it's called. Does anyone have any ideas?