I'm brand new to Macruby and having trouble getting started at even the "Hello World" level. I have the Macruby Peepcode screencast and the beta version of the MacRuby version for O'Reilly. What I've found is that XCode 4.0 is dramatically different then what I saw with XCode 3.0 in the screencast so I'm having trouble following along with the tutorial. Additionally, I also ran into problems trying to run Matt Aimonetti's sample code at https://github.com/mattetti/MacRuby--The-Definitive-Guide.git. I ran into "missing base SDK 10.5", I have 10.6 not 10.5. Can someone suggest a learning strategy with the best available tutorial/documentation? I'm guessing I should try learning with XCode 3.0 because XCode 4.0 is still too new right now?