Pick one of the following problems to do for your interclass problem.
1. Make the person walk randomly around the screen as part of the act method. Look in the API at the Greenfoot class for methods that will allow you to generate random numbers. Note that when you call a static method the syntax is ClassName.methodName(args).
2. Make the person walk in circles. You will do this by having the move based on the rotation of the person and by changing the rotation with each call to act. To get the move from the rotation will require using the trig functions sine and cosine. These can be called with Math.sin(angle) and Math.cos(angle). One catch is that the sine and cosine functions want radians and rotation is in degrees.
3. Have the city start off with ten houses at random locations. See 1. for how to get random numbers.
4. Make the person reproduce. Each time act is called have a new person appear at a random location on the screen. See 1. for how to get random numbers. (Hint: if you do this, don't do Run. Hit Act multiple time instead.)