The game itself is here



You are an alien.
This is your u.f.o.
To control your u.f.o. Simply change its' velocity vector by moving the mouse. The velocity vector which is represented by the blue arrow, has both direction and magnitude.
Its direction dictates in where the u.f.o. will go.
Its magnitude dictates the speed at which it goes there.



This is a sheep.



This is a wolf in sheep's clothing
  As you can see it's quite difficult to tell them apart.
Luckily (as everyone knows) sheep have arrows sticking out of them, showing their velocity vector.
Using your custom u.f.o. 'vector detecting technology' (tm), you can see the vector of wolves dressed up like lamb.
Just fly your u.f.o. around the gaff using the blue vector.
When you are over a sheep you think is not a wolf in sheep's clothing, click, and that sheep will be abducted.
If all real sheep on a level are abducted, you pass to the next level (indicated by a big sheepish number).
You have three lives, each time you abduct a wolf you lose a life. This is because having a wolf on board a sheep carrying u.f.o. is not a very good idea. *cough*. (use your imagination, i didn't have time to do dramatic animations).

This applet should demonstrate that vectors have direction and magnitude (Blue vector), and make it intuitively obvious as to how scalars are different to vectors (scalars don't have direction cf Speed Vs Velocity). Hopefully it should also (over?)expose you to the "i and j" format of representing vectors. You should be able to tell which way a vector is pointing from its i and j values after completing a few levels.
Have fun!