Wohlstand
commented
7 years ago In plan the multi-layer backgrounds which are allows have multiple layers with different parallax coefficient (one image over other). If you mean vertical image splitting to strips which are has different vertical parallax, seems a good idea, but how you understand, will be impossible to have both modes at same time (can be added a flag to toggle h/v magic modes and same list of parallax coefficients will be used for vertical dimension).
We have horizontal magic backgrounds (like Sonic 2 Mystic Cavern Zone from SMBX), why we would not have vertical ones? Examples of usage: for tall towers, deep ravines and canyons and other vertical sections.