Read this and answer the question. If the question is unanswerable, say "unanswerable".

The graphic novel—book-length comics—began to gain attention after Will Eisner popularized the term with his book A Contract with God (1978). The term became widely known with the public after the commercial success of Maus, Watchmen, and The Dark Knight Returns in the mid-1980s. In the 21st century graphic novels became established in mainstream bookstores and libraries and webcomics became common.

In addition to printed graphic novels in stores, what became popular offline?
unanswerable