# draw blue ball
xPos = math.cos(step) * AMPLITUDE
yPos = -1 * math.sin(step) * AMPLITUDE
#yPos = -1 * abs(math.sin(step) * AMPLITUDE) # uncomment this line to make the ball bounce
pygame.draw.circle(DISPLAYSURF, BRIGHTBLUE, (int(xPos) + WIN_CENTERX, int(yPos) + WIN_CENTERY), 20)