nomainwin
    WindowWidth = 400
    WindowHeight = 300

    open "Pendulum" for graphics_nsb_nf as #main
    #main "down;fill white; flush"
    #main "color black"
    #main "trapclose [quit.main]"

    Angle = asn(1)
    DeltaT = 0.1
    PendLength = 150
    FixX = int(WindowWidth / 2)
    FixY = 40

    timer 30, [swing]

    wait

[swing]

    #main "cls"
    #main "discard"

    PlumbobX = FixX + int(sin(Angle) * PendLength)
    PlumbobY = FixY + int(cos(Angle) * PendLength)
    AngAccel = -9.81 / PendLength * sin(Angle)
    AngVelocity = AngVelocity + AngAccel * DeltaT
    Angle = Angle + AngVelocity * DeltaT

    #main "backcolor black"
    #main "place ";FixX;" ";FixY
    #main "circlefilled 3"
    #main "line ";FixX;" ";FixY;" ";PlumbobX;" ";PlumbobY
    #main "backcolor red"
    #main "circlefilled 10"

    wait

[quit.main]
    close #main
    end