This little utility is activated by LeftWindows-LeftMouseClick (LWin & LButton). The window under the mouse cursor is marked as hide-and-seek. After that, if the mouse cursor leaves the window or gets to its border (useful for maximized windows), the window becomes transparent. When the cursor returns to the inside of the hidden window, it becomes opaque again. This behavior remains active and automatically adapts to moved or resized windows, too. Pressing the HotKey: LWin & LButton again de-activates the script and removes the transparency effect from the hide-and-seek window, if it still exists. If the script exits for whatever reason (error or manual exit through the tray icon), the opacity gets restored, so you won't be left with an invisible window.
If the mouse cursor is on the TaskBar at activation, you get a similar behavior as its Auto Hide option. Pressing the HotKey again, regardless of the mouse position, restores the normal taskbar.
OnExit Cleanup LWin & LButton:: IfEqual HideWindow,, { ; Not set => Activate now MouseGetPos,,,HideWindow ; Window ID under mouse SetTimer TransWindow, 150 } Else { ; Already set => Stop, Restore SetTimer TransWindow, Off IfWinNotExist ahk_id %HideWindow%, Return WinActivate ahk_id %HideWindow% WinSet Transparent, 255, ahk_id %HideWindow% HideWindow = } Return TransWindow: CoordMode Mouse, Relative MouseGetPos X, Y, Window WinGetPos,,,X1, Y1, ahk_id %HideWindow% If ( Window = HideWindow && X > 4 && Y > 4 && X < X1-5 && Y < Y1 ) WinSet Transparent, 255, ahk_id %HideWindow% Else WinSet Transparent, 1, ahk_id %HideWindow% Return Cleanup: IfWinExist ahk_id %HideWindow% { WinActivate ahk_id %HideWindow% WinSet Transparent, 255, ahk_id %HideWindow% } ExitApp