Table 2. Examples of independent layers of interactivity.

Plot	Layer	Geom-drawing interactivity	Geom-manipulation interactivity
Scatterplot matrix	Background	None	User hovers over background hexagons to view gene counts
	Foreground	User clicks on background hexagon to draw corresponding genes as foreground points. Background layer does not need to be redrawn	User hovers over foreground points to view gene names
Litre plot	Background	User uses Shiny buttons to specify treatment pairs and hexagon sizes for drawing background hexagons	User hovers over background hexagons to view gene counts
	Foreground	User uses Shiny buttons to specify metric, metric order, and point size for drawing foreground points. Background layer does not need to be redrawn	User hovers over foreground points to view gene names
Volcano plot	Background	User uses Shiny buttons to specify treatment pairs and hexagon sizes for drawing background hexagons	User hovers over background hexagons to view gene counts
	Foreground	User uses Shiny buttons to specify point size, log fold changes, p-values to draw foreground points. Background layer does not need to be redrawn	User hovers over foreground points to view gene names