$(function() {

    var dragging = 0;

    var target     = $('#target');

    var mainTarget = $('#mainTarget');

    var elOfs = mainTarget.offset();

    var cent  = {X: mainTarget.width()/2, Y: mainTarget.height()/2};    

    var elPos = {X: elOfs.left, Y: elOfs.top};

    target.mousedown(function() {

        dragging = true;

    });

    $(document).mouseup(function() {

        dragging = 0;

    }).mousemove(function(e) {     

      if(dragging) {

         var mPos    = {X: e.pageX-elPos.X, Y: e.pageY-elPos.Y};

         var getAtan = Math.atan2(mPos.X-cent.X, mPos.Y-cent.Y);

         var getDeg  = -getAtan/(Math.PI/180) + 135; 

         mainTarget.css({transform: 'rotate(' + getDeg + 'deg)'});

      }

    });

});