         view.draw()
            },
            -1, // run forever, use buttons to start/stop
            30 // 30 fps
        )

        function setShape(shape) {
            view.drawOptions.turtlesShape = shape;
            view.draw();
        }
        const buttons = new Buttons('buttonsDiv', [
            { name: "on/off", cmd: () => anim.toggle() },

            { name: "bug", cmd: () => setShape("bug") },
            { name: "arrow", cmd: () => setShape("arrow") },
            { name: "dart", cmd: