The daily coin puzzle. The Mint wants its money back — free the coins it asks for without leaving a single illegal row behind.
Every row on the table is legal in one of two ways. A run: three or more in sequence, all the same metal. A set: three or more of one number, every metal different. Rows can sit broken while you work — they just cannot be broken when you finish.
One tray a day, in easy, medium and hard variants.