Floor texture scale differs between 2/3 and fullscreen mode

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When switching between 2/3 and fullscreen mode, the relative size of the floor and ceiling textures changes. This is not a new defect and is apparent in the original game executable.

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This one is annoying me because I feel like it's hiding in plain sight somewhere. There's a section in the floor code where there aspect ratio is factored in again but somehow doesn't seem to make a difference even when I comment it out.