How do I find the angle between 2 points in pygame?
Question: I am writing a game in Python with Pygame.  
The co-ords (of my display window) are  
`( 0 , 0 )` at the top left and  
`(640,480)` at the bottom right.

The angle is  
`0°` when pointing up,  
`90°` when pointing to the right.

I have a player sprite with a centre position and I want the turret on a gun
to point towards the player. How do I do it?  
Say,  
`x1`,`y1` are the turret co-ords  
`x2`,`y2` are the player co-ords  
`a` is the angle's measure


Answer: First, `math` has a handy `atan2(denominator, numerator)` function. Normally,
you'd use `atan2(dy,dx)` but because Pygame flips the y-axis relative to
Cartesian coordinates (as you know), you'll need to make `dy` negative and
then avoid negative angles. ("dy" just means "the change in y".)

    
    
    from math import atan2, degrees, pi
    dx = x2 - x1
    dy = y2 - y1
    rads = atan2(-dy,dx)
    rads %= 2*pi
    degs = degrees(rads)
    

`degs` ought to be what you're looking for.

