Grapat Rainbow Nins & Rings & Coins

Where's nin? In this set from Grapat the nins can be completely hidden, and slowly revealed, by the circular rings. How many rings do I need to add to hide the nin? Who will hide theirs first? Will  I  put a coin lid on my pile? What colour goes on top? Lots to do and learn with this simple set. Available in two colours, bright rainbow and soft pastel.