# Game Development:Intro to Computer Science

## CSC 105Union CollegeFall 2009

Exercises about dictionaries and to practice for the final are on Codelab.

Helpdesk in Olin 102, Sun-Thu 7-9pm.

### Drawing Fractals

#### Concentric Circles

First, write a recursive function that draws concentric circles, like this:

To start you can use the following program which draws one big circle at the center of the screen big_circle_v0.py.

Change this program so that instead of drawing one big circle, it calls a recursive function which draws concentric circles as in the picture.

In the recursive case (if the radius is greater than some threshold), this function should draw a circle at the given radius and then call itself recursively with a smaller radius.

In the base case (if the radius is smaller or equal to some threshold), this function should just draw a circle.

Write the code on paper first, then implement it.

#### More circles

Next, write a program that recursively draws this picture:

Figure out what the recursion is, first, and describe it in English. Then, write the code on paper, and only then implement it.

#### Pyramid

Here is another one to try. If you prefer you can also invent your own recursive pattern and write a program that draws it.

Left is a picture of the whole pyramid. The picture on the right shows a close up of the smallest piece - so you can see that the pyramid is built of squares, even though it may look triangular.