screen_size holds the player's screen size
Screen_size starts at 0 if the player has no HUD displayed and then increments by 4 for each time the screen is shrunken, up to 64. A value of 4 means the player has just the mini-HUD displayed. A value of 8 or above means the player has the full status bar up. From 12 to 64, the viewport will shrink, with a texture filling the border. The HUD will remain at full size.
Not to be confused with resolution.