stars_in_the_sky

The idea

Imagine a night sky filled with sparkling stars. This is what I had in my mind and I wanted to replicate it in Python (see Output). (A nice idea to kick start I think :))

Here's what the code is doing

1. Firstly, I created a black drawing screen for my turtle. I called my turtle 'Judith'.
2. In Python's turtle module we have the capability to
   1. Capture Judith's traverse path (we have the control over to capture certain traversed path and leave some as undiscovered for others :). This can be done via penup and pendown methods.)
   2. Instruct Judith in which direction to move and how far to move. This can be done by left, right, forward methods.
   3. All the turtle methods used can be found in the documentation
3. Secondly, I defined a function called star (this is the crux of the code). Let's understand this function. To create a star we will be using equilateral triangles. Keeping things simple, Turtle is at x=0, y=0 (see illustrated image Star heading North).
   1. Judith's head is kept in North direction via setheading(90). She is moved to desired location via setx, sety and her head is oriented left 30 degrees via left(30). Now Judith is facing 30 degrees West of North.
   2. Judith is marched forward distance=20 units. Here Judith's x,y co-ordinates are remembered. We will be using it to find the starting point for our next triangle to complete the star.
   3. Now, Judith is turned right 30 degrees + 90 degrees. She is facing East now. She is marched forward 20 units. Here, mid-point is found between previous x,y co-ordinates and current x,y co-ordinates. Mid-point between $x_1,y_1$ and $x_2,y_2$, $$x = {{x_1+x_2} \over 2}, y = {{y_1+y_2} \over 2}$$. This is the reference point for the starting point of the next triangle.
   4. See illustrated image Star tilted at an angle to get an idea about how the starting point of second triangle is found. I used math.cos and math.sin functions from Python's math module.
   5. Rest all is bread-and-butter, turn and move to complete the second triangle.
4. Finally, I called this star function in for loop to create many stars.
   1. I am generating random x,y (initial locations) to have stars distributed in the sky using randrange from Python's random module.
   2. I defined a variable called factor to get the feel that some stars are distant so they are appearing small.
   3. I defined a variable called ha so that not all stars are headed 90 degrees, some are tilted as well.

Star heading North

Star tilted at an angle

Output