Star field

So we have many things on the screen. Let's move them and try to create something useful. We can draw small circles moving down the screen and simulate a star field.

A bit of theory: conditionals

You may have seen this before, but it's good to refresh our memories. Type down the following program:

number = 4
if number > 10:
  print("The number is greater than 10")
elif number == 10:
  print("The number is 10")
else:
  print("The number is less than 10")

• What does the program do?
• How can you change the first line so that a different message is printed?

Flying though space

We can now use all we have learned so far to create a star field animation. As usual, start a new program from scratch that does the following:

1. Import the random library.
2. Import Pygame.
3. Define a class Star.
4. Create an empty list where we'll put our stars.
5. Write a loop that will run 100 times. Each time it will do the following:
   1. Create a Star object and put it in a variable.
   2. Give the star a random x coordinate, between 0 and 800.
   3. Give the star a random y coordinate, between 0 and 600.
   4. Give the star a random size, between 1 and 3.
   5. Give the star a random speed, between 1 and 3.
   6. Give the star a random brightness, between 0 and 255.
   7. Add the object to the list of stars.
6. Initialize Pygame
7. Create a window of size 800x600
8. Write a loop that will run 500 times. On each iteration, do the following:
   1. Paint the screen completely black
   2. For each star in the list, do the following:
      1. Draw a circle on the screen so that:
         • The radius is the size of the star
         • The colour is the brightness of the star, three times as a list. Eg: if the brightness is 150, the colour will be [150, 150, 150].
         • The position uses the x and y values for the star.
      2. Change the y coordinate of the star so that:
         • If it is less than 600, it increases by 1
         • Otherwise, it is set to 0
   3. Update the screen