Cookie Jam
The classic bakery board: swap two biscuits, clear the icing underneath, work through a level map that stretches further than anyone reasonably needs. What keeps it readable after a hundred stages is the colour work — the sweets are distinct shapes as well as distinct colours, which matters more than it sounds when the board is half covered in jam.
Levels are short. If you have twelve minutes and a coffee, you will finish two or three of them and feel like you got somewhere.