Tap once for a star, again to mark, again to clear
A pure-logic placement puzzle from the Nikoli stable. The grid is carved into irregular coloured regions, and your job is to drop exactly one star into every row, every column, and every region at once — while never letting two stars touch, not even at a corner. Those three overlapping demands lock against each other beautifully: a star that satisfies a region may break a column, and the no-touching rule keeps quietly trimming your options. There is no arithmetic and no luck, only deduction, and every board has exactly one solution that logic alone can reach. Choose a 6×6, 7×7, or 8×8 grid, and race your own best time.
The board is divided into coloured regions, one region for each row of the grid. Your goal is to place stars so that there is exactly one star in every row, exactly one in every column, and exactly one in every region — and so that no two stars are next to each other in any direction, including diagonally.
Tap an empty cell once to place a star. Tap the same cell again and the star becomes a small dot — a private mark you use to say "a star can never go here," which has no effect on the rules and just helps you think. Tap a third time to clear the cell back to empty.
Any star that currently breaks a rule glows red: that means it shares its row, column, or region with another star, or it is touching another star. A correct, conflict-free star stays gold. When you have placed the right number of stars with no red ones left, the board is solved and your time is locked in.
Every puzzle is generated with exactly one solution, and that solution can always be found by reasoning — you never have to guess. Use the grid buttons to switch between a gentle 6×6, a medium 7×7, and a tougher 8×8, each with its own best-time record. Tap New for a fresh board, or Clear to wipe your stars and marks and start the same board over.
Start with the small regions and the edges. A region squeezed into two or three cells gives away far more than a sprawling one, because its star has almost nowhere to hide; and a star near a wall or corner forbids fewer neighbours, so the most constrained spots usually crack first. Find the region with the fewest legal cells and work outward from there.
Mark, don't just stare. The dot is your most powerful tool. Every time you confirm a star, dot out its whole row, its whole column, its region, and all eight cells around it — the picture left behind is what reveals the next forced move. Empty cells are noise; dotted cells are deductions you have already made and won't have to redo.
Lean on the counting, not on trial and error. If a region, row, or column has exactly one cell still open, that cell must hold the star, full stop. Conversely, if placing a star somewhere would leave a region with no room at all, that placement is impossible — eliminate it. Chains of these "only one spot left" and "this would strand a region" arguments solve the whole board without a single guess.
Watch where two lines of pressure cross. The hardest steps come when a region's possibilities and a column's possibilities overlap in just one cell, or when two regions both need a star in the same short strip and so block everything around that strip. Train your eye on intersections of constraints, not on single cells, and the 8×8 boards stop feeling intimidating.