JS: dbg show coords red circle

gistfile1.js

function dbg_showCoords(xy) {
    var size = 500;
    var hsize = size/2.0;
    $("<div></div>").css({
        position: "absolute",
        left: xy.x-hsize,
        top: xy.y-hsize,
        width: size,
        height: size,
        "border-radius": size+"px",
        "background-color": "red",
        opacity: 0,
        "z-index": 4,
    }).appendTo(
        "body"
    ).animate({
        width: 1,
        height: 1,
        left: "+="+hsize,
        top:  "+="+hsize,
        opacity: 0.85,
    }, 300, function() {
        $(this).remove()
    });
}