If you want to make a gauge chart in S3, you’ll need a needle on your gauge. It’s not hard to draw a triangle, but here’s the extra work to rotate it.
Rails asset pipeline allows you to use erb helpers in your CoffeeScript. You’ll still need to bring get these files into Karma runner. It’s really easy. You just need to get to know your Karma config options.
Sinatra is nice because it’s super lightweight. This will allow you to make it do exactly what you want, nothing more. This is the opposite of Ruby on Rail’s convention. Likewise, it takes just a bit more configuration to make Sinatra serve CoffeeScript as compared to Rails.