Isn't there a massive unspoken constraint: you can only have monochrome icons? The sprite they show is impossible to reproduce: look at the "locked" icon, e.g.

Isn't there a massive unspoken constraint: you can only have monochrome icons? The sprite they show is impossible to reproduce: look at the "locked" icon, e.g. It's great now that minimalistic design is in style, but in a year when that fad has passed and my designer wants color again, I'm going to have to completely rewrite my infrastructure back away from using icon fonts.