update the tour

[kaikalii]

I'm not sure modifiers should be added to some of this code.

Although it raises a question about whether things like on/by (and maybe below) should be taught earlier in the tour/tutorial.

[Marcos-cat]

My opinion was that, Because the code got more complicated as it went down, by was not the most complicated thing they would encounter so was fine to include.

[Marcos-cat]

I don’t think they should be taught, but showing them in later examples seemed harmless

[Marcos-cat]

abandoning this until we talk about it further