The sheep themselves vary from normal Pastoral sheep that are docile and easily intimidated to the more aggressive rocker sheep called the Long Wools. You guide the sheep around the levels by effectively pushing them away from your character. If you don't scare them so much they won't go exactly where you want them to, but if you scare them too much they might end up running straight into an obstacle you're trying to avoid, like shark-infested corn or cows on bicycles, and they'll end up as mincemeat. You can't change the herder once you're in the game, so you have to pick one that best suits your style before you start. To make things even harder, you can't leave them alone too long or they'll start wandering about and no doubt end up blundering into something they really shouldn't.
Sheep certainly starts out easily enough.
The training levels teach you everything you need to know and the controls are simple and intuitive, as you might expect. You soon learn the basics of how the sheep react to your character, and get a bit of an idea when to sneak up on them so they don't run off, or when to leggit towards them like a mad man. There are seven different stages which range from a village fete to outer space. Each stage is divided into four levels, and the trick is to find the right breed to use on each level. Graphically, Sheep was never going to set the world on fire but it certainly does the job well enough.