Want to focus on all windows in one application, just select "Application Mode" and click;
Want to focus on a single window, just select "Single Window Mode" and click;
Want to focus on multiple windows in one application or across applications(such as twitting while watch video), just select "Multiple Windows Mode" and click, click...
Want to change the fog's density, just drag/click the density slider until you feel comfortable.
With iFogg, you can easily focus on what you want via simple click(s). No need to frequently do the show/hide anymore.
Want more features, just have a trial on iFogg and let me know your requirement. It could be implemented in the coming updates.