Glad you have something.

How robust does this need to be? Since I didn't recognize your algorithm as any of the usual "point in polygon" algorithms, I tested it against some random polygons, and got several false positives. I suspect that your algorithm works just fine for a subset of polygons, but is not applicable to all polygons. As long as you know that your polygons will always be like your test polygon here, then it's probably okay. If you can't be certain that all of the polygons you need to test will have the same features as your test polygons, you might want to consider a more robust "point in polygon" algorithm.

Again, if you are satisfied, I'm satisfied. To avoid coming back to this again in a few months or years, I recommend testing your point in polygon algorithm sufficiently to make sure it will work for all of the polygons you will need to test.