River Crossing: classic logic with breadth-first search

"River Crossing" is more than the wolf, goat and cabbage puzzle. It is a small solution-search lab where an algorithm stands behind every level.

Three puzzles, three mechanics

Level one is the iconic trio: the wolf eats the goat, the goat eats the cabbage if left together without you. Level two is the missionaries-and-cannibals transport problem, where on either bank cannibals must not outnumber missionaries. Level three is two pairs of wolves and goats, where the boat already holds three — otherwise the puzzle has no solution.

Why it is interesting

Inside the game lives a real BFS solver: pressing "Demo" makes the program explore states (who is on which bank plus where the boat is) breadth-first, pruning dangerous ones, and finds the shortest move sequence. You can win on your own or watch the machine solve it in seven moves.

Where to start

Click a character to put them in the boat, then press "Cross". If a move is illegal the game honestly tells you who would get eaten. Start with level one to feel the rule, then move on to the missionaries.