AJAX loading screen. Make hover create a mark, store hover status. Add dependency graph back + keypress and help to trigger it.
Fix loading screen showing up and staying permanently for new docs. Remove UIDs from save files, so loading save file puts it in the existing doc location. Update all lines after if you delete a line. Dependency graph lies atop text instead of floating away. Make overdetermined systems show 'approx' equality based on epsilon comparison instead of equality. Number widgets now tied to hover mark, instead of managing their own existence. Hover mark goes away when you move the mouse somewhere else; mouseleave wasn't reliable. Cmd/Ctrl trigger dep graph whenever you press them, and the graph goes away when you stop hovering or let go of the key. Make NaN a valid number token.
Clean up keys helper. Make it easier to get to number widget without losing hover focus by enlarging its area. Remove fades to make hover/unhover feel more responsive.
Mousedown goes through to number widget now. Switch pencil and cog icons in number widget so that the visible icon reflects the number's state.