Fortunately, necessity remains the mother of invention, and a lot of the design work that we're the most proud of with the aircraft came out of solving the unique problems of operating it on the ground -- everything from a continuously-variable transmission and liquid-based cooling system that allows us to use an aircraft engine in stop-and-go traffic, to a custom-designed gearbox that powers either the propeller when you're flying or the wheels on the ground, to the automated wing-folding mechanism that we'll see in a moment, to crash safety features.