Backgrounds
Each room can have up to 8 backgrounds. Also it has a background color. All aspects of these backgrounds you can change in a piece of code using the following variables (note that some are arrays that range from 0 to 7, indicating the different backgrounds):
background_color Background color for the room.
background_showcolor Whether to clear the window in the background color.
background_visible[0..7] Whether the particular background image is visible.
background_foreground[0..7] Whether the background is actually a foreground.
background_index[0..7] Background image index for the background.
background_x[0..7] X position of the background image.
background_y[0...7] Y position of the background image.
background_width[0...7]* Width of the background image.
background_height[0...7]* Height of the background image.
background_htiled[0..7] Whether horizontally tiled.
background_vtiled[0..7] Whether vertically tiled.
background_xscale[0..7] Horizontal scaling factor for the background. (This must be positive; you cannot use a negative value to mirror the background.)
background_yscale[0..7] Vertical scaling factor for the background. (This must be positive; you cannot use a negative value to flip the background.)
background_hspeed[0..7] Horizontal scrolling speed of the background (pixels per step).
background_vspeed[0..7] Vertical scrolling speed of the background (pixels per step).
background_blend[0..7] Blending color to use when drawing the background. A value of c_white is the default. Only available in the Pro Edition!
background_alpha[0..7] Transparency (alpha) value to use when drawing the background. A value of 1 is the normal setting; a value of 0 is completely transparent.