from visual import *
ball = sphere(pos=(-5,0,0), radius=r, color=color.red)
wallR = box(pos=(6,0,0), size=(0.2,12,12), color=color.green)
wallL = box(pos=(-6,0,0), size=(0.2,12,12), color=color.green)
wallT = box(pos=(0,6,0), size=(12,0.2,12), color=color.blue)
wallB = box(pos=(0,-6,0), size=(12,0.2,12), color=color.blue)
dt = 0.05
ball.velocity = vector(2,1.5,0)
while 1:
  rate(100)
  ball.pos = ball.pos + ball.velocity*dt
  rate(100)
  ball.pos = ball.pos + ball.velocity*dt
  if not (wallL.x+0.5 < ball.x < wallR.x-0.5):
    ball.velocity.x = -ball.velocity.x
  if not (wallB.y+0.5 < ball.y < wallT.y-0.5):
    ball.velocity.y = -ball.velocity.y