Play: Click a square to place a stone; click the same square again to remove it. Rule: Goal is to maximize stones such that no three lie on a straight line. Lines include any slope (horizontal, vertical, diagonal, or arbitrary).
If placing a stone creates a line of ≥3 stones, the stone is still placed but shown red (invalid) and does not count toward Personal Best. All lines with ≥3 stones are drawn as solid red segments spanning the outermost stones on that line. Collinearity Detection: When ON, every pair of stones generates a faint red line across the entire board (clipped to the edges). Every empty square lying anywhere on those discrete lattice lines is shaded translucent red. Use this to visualize future conflicts; turn OFF for a cleaner view. Symmetric Pruning: When ON, applies D4 symmetry group analysis to the current board state. Detects the stabilizer subgroup (symmetries that preserve placed stones) and prunes equivalent moves via orbit‑based reduction, keeping only the canonical representative (smallest index) in each orbit. Remaining legal moves are shaded translucent green. Show Sample Solution: Loads an optimal solution for the current board size (available for sizes 3-12). Note that solutions are not unique—multiple optimal arrangements may exist. Clicking this button will erase all existing stones on the board and replace them with the sample configuration.
Personal Best counts only valid (non‑red) stones.
Tip: You can paste/export coordinates from the box above to share a configuration.