Green flag puts the project in its initial state, in case you stopped it part way through. The three buttons at the bottom are like those on a DVD. Clicking "special features" lets you choose between the standard version of the project, intended for a general audience, and a longer version with points directed specifically to the Scratch Team.
I wrote this in 2010, when Jens and I released BYOB 3.0. At that time we thought we'd convince the Scratch Team to include first class procedures and lists in Scratch itself, and this project was made mainly as propaganda directed specifically to the ST. The project is way bigger than the allowable limit in the Scratch 1.4 cloud storage, so I also made an abbreviated version, the "BYOB3 trailer," to upload. Eight years later, it's interesting to see how much we got right and how much we got wrong. It didn't take us long to add sprite cloning, in BYOB 3.1. But it wasn't until Snap! 4.0 that we got the notation for procedure-as-data right.
