Keyboard: ↑ ↓ ← → or W A S D. Press Space to reseed the motion field. The visible screen is now a camera into a much larger simulation domain, with a ship-centred soft follow camera so the world clearly scrolls when the ship moves. Boundary button cycles the world-edge behaviour between Open, Wrap, and Reflect. Drive button cycles the background forcing between Ambient and Source→Sink, where flow enters from the right and is drawn out to the left.