What would be the best approach to detect walls or corridors in this game?

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The title pretty much explains my question:

Here is two different screenshot from the game I'm talking about. My task is to find the wall-floor boundary and use it to navigate around programattically.

I've already tried Canny edge detection with blur and colour mask, pattern matching using the wall texture and a contour detection on the grey regions inside walls. Only the latter has given an acceptable result so far, the first method fails in different places around the map, the second didn't work at all. This made me wonder if exists a better, more optimal method to fulfill my goal? I am quite new to opencl and computer vision, so I'd appreciate any hints!