Work 29: Turtle Power!

Interface
- A slider called num_sides
  - Should start at 3 and go to a reasonable number (like 20)
- A slider called side_length
  - Should start at 1 and go to a reasonable number
- A slider called pattern_angle
  - Should start at 0 and go to 360
- For each slider, set the initial value to be something that makes sense, play around with the values to see what works well
- Include buttons for each procedure listed below, pass the sliders as arguments when making the buttons.
Procedures
- setup [n]: observer
  - Clear the screen and make n turtles (you can add custom features to the turtle if you wish)
- regulargon [n s]: turtle
  - Draw a regular polygon with n sides of length s
- pattern [n s angle] : turtle
  - Call regulargon and then turn right by angle degrees.
  - Make the button for pattern a forever button!
- turtle_spread : turtle
  - Have the turtle point up.
  - Set the turtle’s x coordinate to 0
  - Set the turtle’s y coordinate such that:
    - turtle 0 is at the bottom of the world (-16)
    - All other turtles are evenly spaced along the y-axis. This will depend on how many turtles there are.