วิธีเล่น Between Lines Sudoku

Between Lines Sudoku is a variant where lines with circular endpoints are drawn on the grid. Every digit along a line (excluding the endpoint circles) must be strictly between the two endpoint values. The endpoints themselves are placed during solving — only the line positions are given.

The two circles at the ends of each line are the boundary values. Every cell between them must be strictly greater than the smaller endpoint and strictly less than the larger one. You deduce which endpoint is larger as part of the solve.

Yes. Endpoint circles are not pre-filled — you place digits in them during solving. The only rule is that every cell along the line (excluding endpoints) must sit strictly between whatever ends up in the two circles.

Look for short between-lines — a single cell between two endpoints is tightly constrained. Combined with row, column, and box rules, the valid range for that cell is often very small. Also look for lines where available candidates in a given row or column form a narrow range.

The concept is straightforward but the deductions require careful range analysis. Tracking the minimum and maximum possible values for each endpoint and inferring the valid range for in-between cells is the core skill. Easy puzzles make this very accessible.

Easy puzzles take 8–18 minutes. Medium puzzles run 18–35 minutes. Hard puzzles average 35–65 minutes and expert puzzles can take over 90 minutes. Solve time scales with the number of overlapping lines and the complexity of range interactions.