The kanji graph is set at 100vh (full viewport height), which is great when the sidebar is to the side. For narrow devices, Bootstrap moves the sidebar below, and there's no way to scroll it into view (scrolling the graph area just moves the kanji diagram).
Solution will likely be one of:
change graph to 80vh or similar for narrow devices
change responsiveness so that the sidebar never moves below (and recommend holding phone sideways)
The kanji graph is set at 100vh (full viewport height), which is great when the sidebar is to the side. For narrow devices, Bootstrap moves the sidebar below, and there's no way to scroll it into view (scrolling the graph area just moves the kanji diagram).
Solution will likely be one of: