Revealing hidden pictures in Picture Grid, Games by Zaweba

Some puzzles reward you with a number. Picture Grid rewards you with a picture. It is a logic puzzle on the Puzzles shelf of Games by Zaweba, where you fill in squares on a grid using number clues, and when every clue is met a hidden coloured picture appears. Nothing is guessed: every puzzle can be solved by reasoning alone.

Reading the clues

Beside each row and above each column is a short list of numbers. Each number is a run of filled squares in that line, in order. So a row marked 3 1 has a run of three filled squares, then at least one empty square, then a single filled square. Between runs there is always at least one empty square, though there may be more, and there may be empty squares before the first run and after the last.

The puzzle is working out exactly where those runs go, using the rows and columns together.

Filling and crossing out

Click or drag to fill squares. Crossing out matters just as much: when you know a square must be empty, mark it with a cross. Right-click to cross out, or switch to the Cross tool and use an ordinary click. Press X to switch between the two tools.

Crosses are not just tidiness. In this kind of puzzle, knowing where a run cannot go is often what tells you where it must go.

A first strategy

Start with the big clues. In a row of ten squares with a clue of 8, the run of eight must cover the middle six squares wherever it sits, because it can only slide two places either way. Fill those six in. The same overlap trick works for any clue that takes up more than half its line.

Next, look for lines that are already finished. When a row's runs are all filled, cross out the rest of it. Those crosses then help in every column they pass through.

Keep switching between rows and columns. A filled square found from a row gives the column a fixed point, which may settle the column completely, which in turn gives several rows a new fixed point.

Hints, undo and getting unstuck

Press H for a hint, and Z to undo a step. If you have made a mistake somewhere, undo is the tidy way back. When you are stuck, look for a line where the clue sums to nearly the length of the line, or for a line whose ends are pinned down by squares you have already filled. There is always a reasoned next move somewhere.

Picture Grid in Games by Zaweba

Picture Grid sits with Number Place, Hidden Mines and Colour Code on the Puzzles shelf of Games by Zaweba, the puzzles that are solved by deduction rather than reflexes. Its reward is unique on the shelf: when the last clue is satisfied, the grid becomes a coloured picture. That makes it particularly good for a slow evening, or for sharing with someone who likes seeing what the picture turns out to be. Press Esc to pause and F1 for the rules.