Pretty cool! Some feedback that I hope is useful: 1. You seem to be pushing a lot of history entries (as in `window.history`) when opening the Wikipedia pages

Pretty cool! Some feedback that I hope is useful: 1. You seem to be pushing a lot of history entries (as in `window.history`) when opening the Wikipedia pages, but they end up empty when you close the popup so browser back/forward is broken. 2. In my 2560x1440 (`document.body.clientWidth/Height` of 2031x779) the periodic table is higher than the body, which adds a vertical scroll. Not sure if this is intentional, but would be nice if the periodic table was fully contained in the viewport. 3. Related to (2), since the body is taller than my viewport, the Wikipedia popup is overflowing off my viewport, which adds even more scrollbars and I can't properly see the bottom part of the Wikipedia page. 4. There is some right margin somewhere that is adding horizontal scroll (Firefox Windows) For (2) and (3) you might wanna use viewport units (`vh`, `vw`, `vmin`).