GTX turns on a single idea: water held in place by a wall you can't see. A cube-shaped volume of water sits in the middle of the landscape, sloshing and breaking against faces that aren't there, spilling over the top edge but never through the sides. The same setup plays out in two environments, a night rainforest and an open desert, so the barrier stays constant while everything around it changes. The simulation carries the whole piece, which meant the water had to hold its corners under load without reading as a render trick.