If I were involved in the coding, I'd use this as a signal: 1) tab not visible for > 30 seconds 2) then visible with mouse movement a) with

If I were involved in the coding, I'd use this as a signal: 1) tab not visible for > 30 seconds 2) then visible with mouse movement a) within 1 second and b) no scrolling or resizing and c) no keyup (unless it's a modifier key) Things to increase urgency: 1) mouse is moving rapidly upward 2) modifier key keydown occurring Since either one suggests they're about to close it. I'd use the "time away" signal to catch people who switched away from the window, switched back, forgot what they were just reading about (or got sidelined by something new). Just spitballing here.