The Wolf, Goat and Cabbage.
(An 8th-century puzzle)
Take a wolf, a goat and some cabbage across a river. Your rowboat has enough room for the man plus either the wolf or the goat or the cabbage. Don't leave the wolf with the goat alone (because the wolf will eat the goat), or the goat with the cabbage (the goat will eat the cabbage).
Click an item (wolf, goat or cabbage) to place it to your boat and take accross the river.
You win, when all three items are taken to another bank of the river.