Make the "FullScreen" button obvious. Move it to a corner of a showcase.

Currently the "FullScreen" button is on the topbar of the virtual browser.
When a showcase is embedded inside a webpage, the whole virtual browser is very small, so the viewer needs to make the showcase FullScreen. However, at that moment the button is also super tiny, of course. A new viewer might possibly not notice there is a "FullScreen" button existing.

Maybe placing the "FullScreen" button at the right-bottom corner like general video players do is a good choice.