SCREEN 1,320,256,1,1
WINDOW 2,"Pendulum (press any key to quit)",,0,1
PI = 3.1415926535#
theta = PI/2
g = 9.81
l = 1
speed = 0
px = 150
py = 10
bx = 0
by = 0

WHILE INKEY$=""
    LINE (bx-5,by-5)-(bx+5,by+5),0,bf
    LINE (px,py)-(bx,by),0
    bx=px+l*140*SIN(theta)
    by=py-l*140*COS(theta)
    CIRCLE (bx,by),5,1,,,1
    LINE (px,py)-(bx,by)
    accel=g*SIN(theta)/l/100
    speed=speed+accel/100
    theta=theta+speed
WEND
SCREEN CLOSE 1