Drat, I cannot make either of the scripts work, it seems. I don't know why. I even removed #IfWinActive selection, and mapped to left Alt, and still nothing happens. nitrix, I take it those scripts worked for you, right? Odd...
EDIT: Ah, found the culprit. At least on my system, I have to use
WinSet, Transparent, <value>, A
to point at the currently active window. Without it, it refers to Last Found Window, which apparently is not set by anything in the scripts so far (according to docs).