Shadow tilts incorrectly at the top of a slope
if you're on the top of a slope, the shadow tilts incorrectly depending on if you're still on the slope or not. if you're on the slope, the shadow appears flat despite being on the slope, and if you're on flat ground, the shadow tilts as if you were still on the slope.
i think the cause is that the shadow placement logic is checking the wrong side of the linedef to determine if it's on the slope or not (i haven't done any research on this though, it's just guesswork).