Treat the single empty bottle as a loan, not a resource
On a one-spare board, using the empty bottle is unavoidable — but it should always be a loan you can see yourself repaying. Before you pour into it, name the sequence that empties it again. If you cannot, you are not using the bottle, you are spending it.
A practical discipline: park only one colour in it, and prefer the colour that has the most loose single units elsewhere. That way every subsequent unit of that colour has a home, and the bottle is on a path to becoming a finished bottle rather than a dead end.
Keep a legal pour in reserve at all times
Two bottles showing the same colour on top with space available is an escape hatch: a move that is guaranteed to exist next turn. Losing your last such pair, while your only empty bottle is committed, is the exact moment most hard boards become unsolvable — several moves before the game tells you there are no pours left.
When you are deciding between two good pours, prefer the one that preserves a matching pair elsewhere on the board.
Order pours so colours stay recoverable
Two sequences can use the same pours and end in different places, because the intermediate states differ. The general ordering rule:
- Free pours first (whole-block merges that need no extra space).
- Pours that empty a bottle next.
- Pours that expose a buried colour you have a plan for.
- Pours that commit universal space, last, and only with the repayment identified.
A corollary that catches strong players: do not finish a colour early just because you can, if that bottle could have served as a buffer for two more moves. A finished bottle is safe but inert.
Count the deepest unit, not the messiest bottle
Boards often look hardest where they are most mixed, but the real constraint is the single deepest buried unit — the one with the most distinct colours stacked on top of it. That unit tells you the minimum parking space the board will ever demand from you. Work out where each of those covering units is going before you commit space anywhere else.
Use the hint as an audit tool
The hint on the game page returns the first move of a genuine solution from your current position, computed by a solver. That makes it more useful after the fact than during play:
- Decide your move, then press hint. Agreement means your reading was sound.
- Disagreement is the interesting case: the solver's move usually preserves space or keeps a colour recoverable in a way yours did not. Work out which.
- If the hint reports that the position cannot be solved, your last few pours are the suspects. Undo back and try the branch differently — this is the cheapest way to learn which pours actually kill boards.
Aim for shorter solutions once you can solve reliably
There is no move counter to satisfy, but self-imposing one is good practice. Solve a level, note the move count, restart and try to beat it. Shorter lines almost always come from removing partial pours and from finding one chain that empties a bottle instead of two pours that tidy tops. It is the fastest feedback loop available without any external tool.
Know when a restart is the strong move
Undo is for a single misjudged pour. If you have made four or five pours since the mistake, a restart with the knowledge you now have is usually faster and teaches more — you get to test your plan from move one instead of salvaging a position you did not intend to reach. There is no penalty for restarting on this site.