let winsize;
    const calcWinsize = () => winsize = {width: window.innerWidth, height: window.innerHeight};
    calcWinsize();
    window.addEventListener('resize', calcWinsize);

    const getMousePos = (ev) => {
        let posx = 0;
        let posy = 0;
        if (!ev) ev = window.event;
        if (ev.pageX || ev.pageY) {
            posx = ev.pageX;
            posy = ev.pageY;
        }
        else if (ev.clientX || ev.clientY) 	{
            posx = ev.clientX + body.scrollLeft + docEl.scrollLeft;
            posy = ev.clientY + body.scrollTop + docEl.scrollTop;
        }
        return {x: posx, y: posy};
    }

    let mousePos = {x: winsize.width/2, y: winsize.height/2};
    window.addEventListener('mousemove', ev => mousePos = getMousePos(ev));