Kakuro

Medium kakuro uses 8 to 10 cell grids with more entries and more interconnections. The grid is larger, so you need to track more constraints simultaneously. Cross-entry elimination becomes essential: each white cell sits at the intersection of a horizontal and vertical entry, and combining both constraints often narrows candidates to one or two digits.

When straightforward elimination stalls, try working backward from entries that are almost complete. If an entry has one or two empty cells, calculate what digits are needed to reach the target sum, then check whether those digits conflict with crossing entries. This targeted approach is faster than scanning the entire grid.

Ready for a bigger challenge? Try hard.