Nice work, this is a great way of seeing wikipedia + wikidata side by side (and having more intimate access to wikidata IDs).
It would be great if the hierarchy (breadcrumbs) + context of your session were preserved as you are navigating. Right now, it appears the value of this browser is that it augments a wikipedia-type page with wikidata semantic values within a side bar.
In contrast,
http://math.mx (read: mathematics) is an example DAG (directed acyclic graph of hierarchical math topics, presented as a d3 zoomable treegraph) which preserves the context of your session (with breadcrumbs) as you traverse the directed graph of knowledge. A core value proposition of a browser (e.g. web browser) is that the provenance and history of a session is preserved; you can go back and revisit links (history), as well as gain perspective about how your searches were related (provenance). You session, itself, is essentially a graph (and this graph is critical for understanding your coverage/level of comprehension of a domain).
On WikiBrowser, one was viewing the WikiBrowser "Earth" page and you click the inner term "Planet", I would expect the interface to semantically zoom out of "Earth", into planet (because of the directionality of the relationship of the two terms: earth, planet). From this screen, I would expect to be able to go back (close "Planet" and return to "Earth") allowing my context to be returned/zoomed back to "Earth" (which had remained on the stack), or visit a new link/direction from within "Planet" and increase the depth of my stack.
Even with this (linear 1-step browsing w/ a provenance trail) solved, it's often extremely difficult to get a holistic view (topic depth > 1) of a topic (i.e. understand all the topics and sub-topics entailed) just by looking a single wikipedia page. Ideally, one could press a special hotkey (see "
bring and go") and see an overlay (similar to your sidebar) with a graph (link depth of ~2 pages) which shows an entire graph of a page / topic's wikidata or wikipedia relations, which you can then use to navigate and more efficiently explore the knowledge space.
On the other hand, if (instead of a "browser") your main goal is augmenting (and creating a bi-directional mapping between) wikipedia articles and wikidata entries, have you considered something like a native Wikipedia Tool, e.g. Navigation Popups? (see:
https://en.wikipedia.org/wiki/Wikipedia:Tools/Navigation_popups -- Under the "Browsing" section, there is a checkable option for, "Navigation popups, article previews and editing functions popup when hovering over links)
It would be great if hovering over hyperlinks in Wikipedia resulted in a community approved 1-line distilled answer / summary tooltip
Just food for thought, to fuel your mission. Good luck!