Every puzzle in Puzelo has exactly one solution — you never have to guess. Pick a type to jump to its rules.
Fill the grid so every row, column and 3×3 box holds the digits 1 to 9 exactly once.
Look for the row, column or box that already has the most digits. If eight of nine cells are filled, the ninth is forced — no thinking required. Work those first; each one you fill makes the next easier. Only when nothing is forced any more do you look at a single empty cell and ask which digits its row, column and box still allow.
The trap is guessing. A well-made sudoku never needs it: at every point there is at least one cell you can determine with certainty. If you find yourself trying a digit to see what happens, you have missed something simpler somewhere else.
Numbers along the edges tell you which blocks of cells to fill. The picture emerges as you go.
Start with the longest runs. In a line of ten cells, a run of eight can only sit in three positions — and the six cells in the middle are filled in all three. That overlap is certain before you know anything else. Mark those, then look at what the neighbouring lines now force.
Most people only fill cells and never mark the empty ones. That is why they get stuck: the empty marks are what turn a vague line into a certain one.
Fill the grid with zeros and ones — never three of a kind in a row, and every row and column balanced.
Find any two identical digits side by side — the cells on both ends of that pair are forced to be the other digit. Then look for gaps: a single empty cell between two identical digits must be the opposite one, or you would create a triple.
The balance rule is easy to forget. Once a row has all its zeros, every remaining cell in it is a one — regardless of what the neighbours suggest.
A crossword with digits: every run must add up to the number in front of it, without repeating a digit.
Hunt for runs with only one possible combination. Two cells adding to 3 must be 1 and 2. Three cells adding to 6 must be 1, 2 and 3. Four cells adding to 30 must be 6, 7, 8 and 9. Where such a run crosses another, the intersecting cell often has just one digit that works in both.
Knowing the combination is not the same as knowing the order. Fill a cell only when the crossing run leaves exactly one option.
A latin square with greater-than signs: every number once per row and column, and every sign must hold.
Follow chains of signs. In a 5×5 grid, three cells linked as a < b < c mean a is at most 3 and c is at least 3. A cell at the small end of a long chain is often forced to 1 — and that single certainty usually unlocks its whole row.
The signs constrain more than they seem. Before trying numbers, read every chain end to end and note the smallest and largest each cell can still be.
Buildings of different heights: the numbers around the grid say how many you can see from there.
The extreme clues are free. A 1 means the tallest building stands right at that edge. A clue equal to the grid size means the row climbs in order: 1, 2, 3, 4, 5. Fill those rows first, then use them to constrain the columns they cross.
A clue of 2 does not mean the second building is tall — it means exactly one building blocks the view of all the rest. Counting visibility, not positions, is the whole skill.
Place one lantern in every row, every column and every coloured region. No two lanterns may touch, not even diagonally.
Look for the smallest region. A region of two or three cells must hold a lantern, so every other cell in those rows and columns is out. Then mark the cells around each placed lantern: a lantern rules out all eight neighbours, and with them often a whole region's remaining options.
Regions that fit inside a single row or column are gifts: their lantern takes that row or column, so no other region may place one there. Tap once for a lantern, twice for a cross to remember where nothing can stand.