Games Programming Source Presentation Setup Prerequisites If you’re using RVM, make sure you switch away from any gemset: rvm use default or rvm use system Note For some reason, when you use the system Ruby on Fedora, you also have to add the json gem to the Gemfile. Install The following will install the gems into the project. rm -f Gemfile.lock bundle config --local github.https true bundle --path=.bundle/gems --binstubs=.bundle/.bin Build, with Rake bundle exec rake