A 5x5 board rated tricky, level 21 of 300. Catdoku levels are identical for every player, so this solution always matches the board in your game.
The level 21 board
Place one cat in every row, every column and every colored patch. No two cats may touch, not even diagonally.
Level 21 answer
Row 1: column 2, in the yellow patch
Row 2: column 5, in the sky patch
Row 3: column 3, in the rose patch
Row 4: column 1, in the mint patch
Row 5: column 4, in the lilac patch
How to solve level 21, step by step
After every placed cat, cross out the rest of its row, its column, its patch and the four corner squares around it. The steps below assume you do (the in-game auto-paws assist does it for you).
Every free square of the rose patch sits in column 3, so the rose cat must come from there and the rest of column 3 can be crossed out. Every free square of the lilac patch sits in column 4, so the lilac cat must come from there and the rest of column 4 can be crossed out. Every free square of the yellow patch sits in column 2, so the yellow cat must come from there and the rest of column 2 can be crossed out. A cat at row 1, column 1 would leave column 2 with no home for its cat, so cross that square out. A cat at row 2, column 1 would leave column 2 with no home for its cat, so cross that square out. A cat at row 2, column 2 would leave column 3 with no home for its cat, so cross that square out. Cat 1 of 5: the yellow patch is down to a single free square at row 1, column 2, so its cat settles there.
Cat 2 of 5: the rose patch is down to a single free square at row 3, column 3, so its cat settles there.
Cat 3 of 5: the lilac patch is down to a single free square at row 5, column 4, so its cat settles there.
Cat 4 of 5: the sky patch is down to a single free square at row 2, column 5, so its cat settles there.
Cat 5 of 5: the mint patch is down to a single free square at row 4, column 1, so its cat settles there.