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"""
 Show how to do a radar sweep.

 Sample Python/Pygame Programs
 Simpson College Computer Science
 http://programarcadegames.com/
 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)

    # Dimensions of radar sweep
    # Start with the top left at 20,20
    # 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()