Ruby extension library for visualizing the line that is currently running
$ gem install wisp
$ rake build
$ ruby -rwisp examples/loop.rb
== Sinatra/1.3.2 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.3.1 codename Triple Espresso)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:4567, CTRL+C to stop
And then open http://localhost:4567 in Google Chrome (recommended) or Firefox.