The style is applied through CSS. The CoffeScript is unobtrusive. The template and the sever logic are distinct (but there's an indentation error in the request handling code).
It's about logical, not necessarily physical separation. For small apps, having everything in one place is actually very convenient.
See also _why's Camping: http://camping.rubyforge.org/ (nowadays maintained by judofyr a.k.a. Magnus Holm)