Working Through a Sheet of 5x5 Grids
Chains are the key at this size: when two signs point the same way along a row, the three cells run in order, so a 4 or a 5 can never open such a chain and a 1 or a 2 can never close it. Combine that with the places left for a 5 and a 1 in each row, and most grids open within a few moves.
What Changes Between the Levels
The levels differ by their clues, not by their size. Easy grids give a head start of four digits and five signs; medium grids keep only the clues needed for a unique answer; hard grids give no digit, so every deduction starts from a sign.
Why Choose Four Grids per Sheet
Four 5x5 grids fit comfortably on A4 and leave room for small candidates, which makes a sheet a good daily set for a commute or a class. For a single large grid per sheet, the 5x5 Futoshiki page is the one to print.