Mobile is a different ball game. To start with, while hardware is more varied it's also got far more standardised input hardware - there's a keyboard and there'

Mobile is a different ball game. To start with, while hardware is more varied it's also got far more standardised input hardware - there's a keyboard and there's a mouse and you can rely on that being the primary input. On Android there will be a touch screen, but it's size, resolution and accuracy will vary. There may be buttons but their quantity and makeup will vary. The second factor is that you cannot get away with bad UI as much as you can on the desktop. On the desktop it's frustrating but survivable, on mobile it's a death knell. It'd be more accurate to call it write once, run poorly everywhere.