The Kano Model is a theory of customer satisfaction developed by Professor Noriaki Kano. It divides a product into sets of of attributes to describe how a customer relates to them.
The model identifies three attribute types: threshold (or 'requirement'), linear (or 'feature') and delightful (or 'delight') and posits that over time many attributes transition from delightful through to threshold as customer expectations raise.
This is particularly true within existing game genres, which is why genres often become an arms race between a few key players.
