> Any advice?
Under what license was the original published? If it was an open-source license, and if the copy includes your copyright notice, then there's no wrongdoing and nothing you can do.
If it was an open-source license and your copyright notice is not present, and if there is any line-by-line copying from your original to the copy, you should be able to prove that the copier simply copied and pasted your code. This kind of copying can be proven using textual matching and the mathematical improbability of an inadvertent exact copy.
If the work was published under anything other than an open-source license, it shouldn't have been published in any way that could be copied (i.e. in source-code form). In this case, any substantial copying is a violation, but you would have a very hard time pursuing a legal remedy.
> I am not sure about html-part, but in terms of design it's copy.
If we're talking about design, not code copying, things become more difficult. Ask yourself how obvious to a practitioner of the art the layout and functions are. To pursue a legal remedy, you would have to show something unique about your design that sets it apart, and you would have to show that someone copied your specific work as opposed to copying the general design principles of similar programs.