Hello Dominique,
the code you provided works great for me, but I'm having problems with the padding of the dragable images (the padding is always 5px on each side, no matter how I try to change it). I tried many possible solutions like below, but nothing works for me:
$(".group1").css("padding", "0px");
$(".group1").each(function() { this.style.setProperty("padding", "0px", "important"); });
I successfuly made images transparent etc., but on the picture below, you can see why the exact image size (without padding) is important to me. On the image below, there is a background image with just the axis and transparent image of the signal dropped on top.
Another (probably similar and somehow related) problem is the size of the drop zones - they are just slightly bigger than the dragable image (rectangle with yellow shadow).
Is there a way to change those properties just for one question in a similar way or not?
Any help will be much appreciated.