```"""
Show how to do a radar sweep.

Sample Python/Pygame Programs
Simpson College Computer Science
http://simpson.edu/computer-science/

"""
# Import a library of functions called 'pygame'
import pygame
import math

# Initialize the game engine
pygame.init()

# Colors
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)
BLUE = (0, 0, 255)

PI = 3.141592653

# Set the height and width of the screen
size = [400, 400]
screen = pygame.display.set_mode(size)

my_clock = pygame.time.Clock()

# Loop until the user clicks the close button.
done = False

angle = 0

while not done:
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True

# Set the screen background
screen.fill(WHITE)

# Width/height of 250
box_dimensions = [20, 20, 250, 250]

# Draw the outline of a circle to 'sweep' the line around
pygame.draw.ellipse(screen, GREEN, box_dimensions, 2)

# Draw a black box around the circle
pygame.draw.rect(screen, BLACK, box_dimensions, 2)

# Calculate the x,y for the end point of our 'sweep' based on
# the current angle
x = 125 * math.sin(angle) + 145
y = 125 * math.cos(angle) + 145

# Draw the line from the center at 145, 145 to the calculated
# end spot
pygame.draw.line(screen, GREEN, [145, 145], [x, y], 2)

# Increase the angle by 0.03 radians
angle = angle + .03

# If we have done a full sweep, reset the angle to 0
if angle > 2 * PI:
angle = angle - 2 * PI

# Flip the display, wait out the clock tick
pygame.display.flip()
my_clock.tick(60)

# Be IDLE friendly. If you forget this line, the program will 'hang'
# on exit.
pygame.quit()

```
﻿