Medium 30×30 Picross — 60-Line Cross-Referencing Across 900 Cells

Medium 30×30 Picross is a 150–240 minute session of sustained cross-referencing across the largest constraint network on the platform. With 60 lines to manage, a first pass that resolves approximately 250–360 of 900 cells, and eight to fourteen full pass cycles required before the grid resolves completely, this is the most extensive non-enumeration Picross session available anywhere.

What "Medium" Means at 30×30

In a 30-cell line, any single-block clue of "15" or smaller produces zero overlap. Medium 30×30 configurations include a significant number of such lines in both row and column directions — configurations where single-block clues of "12", "13", "14", or "15" must accumulate extensive cross-referenced data before any of their cells can be confirmed.

The first overlap pass on a Medium 30×30 resolves 250–360 cells — 28–40% of the grid. Each subsequent pass adds cross-referenced constraint data that progressively reduces the valid arrangement counts of the high-slack lines. The pattern is the same as at smaller Medium sizes, but the number of lines managing simultaneously, the number of passes required, and the total session time are all proportionally greater.

The Medium 30×30 Solving Approach

Step 1 — Overlap pass: Process all 60 lines with line-tracking checklist. Mark every direct result. Categorise all lines that produced zero confirmed cells as "cross-referencing dependent" — these require multiple perpendicular passes before their arrangement counts will be reduced enough to confirm any cells.

Step 2 — Structured propagation: After every confirmation, immediately update the perpendicular line's constraint state. At 30×30, every confirmed cell interacts with 30 perpendicular constraints — the cascade opportunity from immediate propagation is the largest of any grid on the platform.

Step 3 — Priority ordering: At the start of each pass cycle, process lines in priority order: first, any cross-referencing-dependent line that received five or more new perpendicular confirmations since its last processing; second, all other lines by standard order. This ordering consistently produces more confirmations per pass than sequential processing at this grid size.

Step 4 — Repeat: Continue until all 900 cells are resolved. No enumeration, no hypothesis. Eight to fourteen pass cycles of disciplined cross-referencing is sufficient throughout.

Multi-Session Approach at Medium 30×30

At 150–240 minutes, Medium 30×30 is naturally a multi-session format for many players. Stopping at any completed pass boundary is clean — the grid state (all confirmed cells and X-marks) is the only documentation needed for a reliable resume. Because no hypothesis or enumeration records are involved, resuming a Medium 30×30 session is straightforward: verify the grid state against any saved record, process any lines that may have accumulated new perpendicular data since the last session, and continue with the next full pass cycle.

Ready to Progress?

→ 30×30 Hard — arrangement enumeration across 900 cells

→ 30×30 Easy — if Medium feels too large a commitment, Easy builds the 60-line systematic pass habits Medium requires

→ 25×25 Medium — the same cross-referencing approach at the next scale down

Stuck? The 30×30 Solver identifies your next step.