from cs1lib import *
from random import randint, uniform

def circle_art():
    set_clear_color(0, 0, .3)
    set_fill_color(.5, .8, 1.0)
    set_stroke_color(1, 1, 1)

    # create a new bubble every few seconds
    #  (note: better to use a named constant than .025)
    if uniform(0, 1) <= .025:
        x = randint(0, WINDOW_WIDTH - 1)
        y = WINDOW_HEIGHT + RADIUS
        xc.append(x)
        yc.append(y)

    clear()
    # your code here; draw and move all the circles
    for i in range(len(xc)):
        draw_circle(xc[i], yc[i], RADIUS)
        yc[i] -= 1

RADIUS = 10 # radius of circles
WINDOW_HEIGHT = 200
WINDOW_WIDTH = 200
FRAME_RATE = 20

xc = []     # empty lists to store
yc = []     #  circle centers


start_graphics(circle_art, 1600, framerate = FRAME_RATE)