6 × 6 is the everyday casual Kakuro size: big enough that runs start to interlock in interesting ways, small enough to finish over a coffee. You will meet more three- and four-cell runs here, which widen the space of digit combinations and reward knowing the unique ones — 6-in-three is always 1+2+3, 30-in-four is always 6+7+8+9.
The habit to build at this size is cross-referencing: a cell's value must satisfy its across clue and its down clue at once, and intersecting the two combination lists often leaves a single digit. Tap any clue in the player to see its live combination list, or study the full combination tables.
Warm up with the daily Kakuro, or step up to 8 × 8 boards when six-wide feels routine.