The games and toys have different degrees of difficulty, graded 1,2 and 3. Some are a little easier and are great to begin with. Some games are a bit more difficult, and some are more advanced and are excellent to use for dogs that need extra mental stimulation.
For beginners, puppies, older dogs and dogs that are difficult to motivate.
Medium, fits most dogs.
Advanced, for "smart" dogs and dogs that need extra mental stimulation.