Everything makes sense in my head. I don't understand why when I click on the button it does not work. I believe the problem is in these text lines
mouse = pygame.mouse.get_pos()
if mouse[0] >= rand_x <= player_size and mouse[1] >= rand_y <= player_size:
sys.exit()"""
In this statement:
mouse[0] >= rand_x <= player_size
what you are really saying is:
mouse[0]>= rand_X and rand_x <= player_size
So if rand_x is not lower or equal than player_size (50) it wont evaluate to True.
The documentation says:
Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false).
Maybe what you meant is:
rand_x <= mouse[0] <= rand_x+player_size
