Thanks for the report, that is very odd. It sounds like the mouse position might be offset. I haven't ran into this yet when testing Chrome on Windows 10, but I'll take another look. Sorry about that!
Sorry to hear that! I have an up-to-date iPad Air 2 and I've tested playing in Safari quite a bit. The touch accuracy is a little annoying and dragging the background unintentionally occasionally happens. I think I can improve this by increasing the touch area around pieces to be a bit more forgiving. Thank you for reporting.