Hi! Yes, it happens once starting and continues throughout the game. It looks like parts of a giant square black box overlapping with the actual skybox. I google it a bit, but no luck finding a possible cause. I'm in Windows 7 (x64) and have a Intel Graphics, just in case you find it to be relevant. Please tell me if you ever find the cause! :D Hehehe, yes, I was wondering if all places were actually toxic (so the game is about never stop running and maximizing your time in higher elevations ) or if one could 'rest' at the top of mountains. Maybe you could add more explicit indications, either of health levels (a bar?) or the toxicity level instead of the elevation. Another possibility would be to represent toxicity hazards with visual cues in the terrain (textures, objects).