Here's a game that will bring back happy memories for those who played its spiritual father, Sheep, about a decade ago.
In this game, you control a sheep dog that has to gather all the sheep and lead them to the light green area. There are different types of sheep: those that come willfully towards the dog, those that try to attack the dog (so they have to be dodged), and those that go the opposite direction from the dog. Also there's a wolf at some levels that tries to grab the sheep for lunch, so you must be on your toes. Later levels also feature lakes (the sheep will drown), switches (you have to put one or more sheep depending on the switch to open doors), and barbwire (the dog loses health upon touching it).
In its essence, it's a tracking sprites routine with cutey graphics, sound that tries to resemble 8 bit machines (thankfully not as annoying as most tunes of that genre are), and really good playbility and level design. Give it a go!