FADE command gives you screen dimmer.
FADE RGB(X,0,0,0) makes whole screen darker or brighter.
The bigger X is, the darker screen is.
The range of X is 0-255.
FADE RGB(X,0,0,32) will give you a transparent dark blue.
I think as follows.
#1: You don't need 'VAR RES=', 'VAR A=', VAR AS=' nor 'VAR ATRB=' in line 13-16.
#2: You need to write '=' instead of '-' in line 13-22.
#3: You don't need '-' in line 25-28.