Sometimes when I'm tired of coding and thinking about the same problems for a while, I still catch myself in managing to focus on a game of Sudoku on the phone

Sometimes when I'm tired of coding and thinking about the same problems for a while, I still catch myself in managing to focus on a game of Sudoku on the phone while having a break. Maybe I'm just using a different part of the brain to do this, so the other part used for programming really gets a break? Just like you can't manage to do any more squats when training, but still can do lots of bench presses?