It is a floating widget on a upper right cornet of a screen. You swipe it left, but don't release a finger, and a list of recent apps will appear. The most recent app is always on the top of a stack. Then moving finger up or down you highlight a desired app you want to bring back to a foreground. By releasing a finger a selected app will be restored. On the first run Gardine will request an "Accessibility service" permission in order to track switch between applications and a permission to display as a floating widget above all other windows.