Const PI = 3.141592920
Dim As Double theta, g, l, accel, speed, px, py, bx, by
theta = PI/2
g = 9.81
l = 1
speed = 0
px = 320
py = 10
Screen 17 '640x400 graphic
Do
    bx=px+l*300*Sin(theta)
    by=py-l*300*Cos(theta)
    Cls
    Line (px,py)-(bx,by)
    Circle (bx,by),5,,,,,F
    accel=g*Sin(theta)/l/100
    speed=speed+accel/100
    theta=theta+speed
    Draw String (0,370), "Pendulum"
    Draw String (0,385), "Press any key to quit"
    Sleep 10
Loop Until Inkey()<>""