background_index[0...7];
Returns: Real
As with most resources, backgrounds can be assigned and changed
by setting their index to a different game asset. This array is
what you must use to change any one of the 8 possible backgrounds
(numbered form 0 - 7 within the array) that a room may have, or to
get the index of any of those backgrounds. When setting it you
should use the index of the included image asset from the
background resources, or, if you have loaded a background into the
game using background_add(), the variable
where you have stored the loaded background index. The value array
for any one of the backgrounds can be set to -1 to remove the
background.
background_index[0] = choose(bck_Day, back_Evening, bck_Night);
The above code will set the background(0) index of the current room to be one of three possible background images from included the assets.