A weak puzzle walkthrough records every input. A stronger one explains why the board refuses to move. That distinction matters in traffic-sorting puzzles, where a correct tap can still be useless if a garage exit, crossing lane, or temporary holding space remains blocked. I used Car Sort level 13 as a small case study for a better hint model. The useful unit is not “tap car number seven.” It is a dependency: this vehicle cannot leave until that lane opens; that lane cannot open until a matchi...