Animating spiral

Hey Everyone! I am a beginner in Processing and I have a homework to do which has to be done till friday xdd The point is I dont know what to do and I need your help :d
Here is the final result how it should look like.

The point starts at a random position on the screen.
The point color is initially randomly selected from an interval around a hue value.
The closer the point is to the center, the smaller it is drawn. It has a size of 20 pixels at the edge of the screen, 1 in the middle of the screen.
When the point reaches the center, it disappears and a new random point is created somewhere on the screen. (Or its properties are reset to look like new)