Fill every empty cell with a number so that each connected group of N cells contains exactly the number N.
A connected group of the same number must contain exactly that many cells. For example, three 3s connected orthogonally form a valid group.
Two different groups of the same number cannot be orthogonally adjacent. Same-number groups must always be separated.
Tip
Fillomino-style region partition puzzles train spatial reasoning, constraint satisfaction, and working memory simultaneously. Research shows that multi-constraint puzzles are effective at improving cognitive flexibility and executive function.