# Detects if two "characters" moving around the screen collide.
#
# The character positions are represented with:
#   character1x, character1y
# and 
#   character2x, character2y
#
# Their movement is represented with:
#   character1x_speed and character2x_speed
#
# The characters are drawn as simple circles.
# And they only move left / right.
#
# Collision is detected with the dist() command, and when they
# "collide" the screen is flashed red for one frame.

character1x = 175
character1y = 200
character2x = 195
character2y = 200

character1x_speed = 3
character2x_speed = -3

def setup():
    size(400,400)

def draw():
    background(255)
    
    global character1x, character2x
    global character1x_speed, character2x_speed
    
    ellipse(character1x,character1y,25,25)
    ellipse(character2x,character2y,25,25)

    character1x = character1x + character1x_speed
    character2x = character2x + character2x_speed

    if character1x > width or character1x < 0:
        character1x_speed = character1x_speed * -1
    if character2x > width or character2x < 0:
        character2x_speed = character2x_speed * -1
        
    if dist(character1x,character1y, character2x,character2y) < 10:
        background(255,0,0)