“When they fall apart it’s usually for one of three reasons: You focus on making one amazing thing but forget that it has to be part of a single, fluid experience. [See also: Figure 3.1.1, in Chapter 3.1.] So you ignore the million little details that aren’t as exciting to build—especially for V1—and end up with a neat little demo that doesn’t actually fit into anyone’s life. Conversely, you start with a disruptive vision but set it aside because the technology is too difficult or too costly or doesn’t work well enough. So you execute beautifully on everything else but the one thing that would have differentiated your product withers away. Or you change too many things too fast and regular people can’t recognize or understand what you’ve made. That’s one of the (many) issues that befell Google Glass. The look, the technology—it was all so new that people had no idea what to do with it. There was no intuitive understanding of what the thing was for. It’s as if Tesla decided out the gate to build electric cars with five wheels and two steering wheels. You can change the motor, change the dash—but it still has to look like a car. You can’t push people too far outside their mental model. Not at first.”