Water jug puzzle rules

Measure the target amount in either jug using only full fills, full empties and complete pours.

Three legal operations

1. Fill A or Fill B fills that jug to its stated capacity from an unlimited tap.
2. Empty A or Empty B drains the entire jug.
3. Pour A into B, or B into A, transfers water until the source is empty or the destination is full.

You cannot choose a partial fill or stop a pour halfway. For example, pouring a full 3 L jug into a 5 L jug already holding 4 L moves 1 L. The result is 2 L in A and 5 L in B.

Controls and completion

Each button performs one operation. Disabled buttons would leave the amounts unchanged. While the action buttons have focus, keys 1–6 select Fill A, Fill B, Empty A, Empty B, Pour A into B and Pour B into A.

Undo removes the last operation. Restart clears this puzzle after confirmation. Any jug holding exactly the target completes the puzzle; choose Next puzzle to continue.

One-step hints

Hint explains the next legal operation on a shortest route from the current amounts. Apply this pour performs only that operation. The shortest start count gives a target to improve your route; longer valid routes still win.

The fill/empty/transfer convention was checked against Math Is Fun’s Jugs Puzzle. Pourhaven’s challenge sequence, art and interface are original.