Thank you to [anonymous] for coming up with this visualization idea.
Each node represents a grid state, and each edge represents an action a user took to modify the grid. Thicker edges and nodes represent multiple users.
starting grid
correct grid
incorrect submission
↗ edit
↗ flood fill
↗ paste
↗ copy from input
↗ resize output grid
↗ reset output grid
(hover over nodes in the graph to show that node's grid)