I have a tank game for a computer applications class. the tank can shoot enemies and destroy them and get points in the fastest amount of time possible. How do i make power ups?. I already have the energy capsules which are the power ups, but i want to know how to make it so if the tank touches or rolls over a energy capsule it will randomly do one of the following so that the same capsule doesn't do the same thing every time:

make tank bigger
make tank smaller
add point to score
and destroy the tank