Once upon a time, there was a Holiday party where many people got very sick.
A young doctor, you, wants to save his friends, now patients, by fighting the disease.
You found the most effective way for that - shrink yourself, and exterminate viruses and germs from inside.
Your mission: travel through your patients body, destroying evil viruses and germs, and saving the good blood platelets.
Hint: some doors are locked and require keys. You will see the keys after scoring enough points.
Good luck, micro-Doctor!
And, dont tickle your friend too much. :-)