hello,

1.     void trace(color[] pix, int sy, int ey)


he's is just saying: the 1st parameter for the function is an array called pix of type color. That's what [] is for: array. Later he says


1. pix[py*width+px] =c;


where you can see that pix is an array.

But that's clearly one of the hardest programs - it's beautiful!


... it appears that writing "for" loops works well without {} or even ; after it, and it then just runs the following line in virtual {} - but I cannot find any of that in the official documentation.

That's right:

1. for....
2.    println ("hello");

gives you 10x hello

1. for....    ;
2.    println ("hello");

gives you 1 hello because for does only what is between for (...) and ;
which in our case is nothing!

Same with if :

1. if (.......)
2.    println ("hello");

works, but


1. if (.......);
2.    println ("hello");

doesn't - hello will always appear.

Since working with { } here is more robust I recommend always using  {}.
Robust means: When you change something, e.g. insert a comment with //... in a separate line then with {} it still works, without {} no more.


Btw.
If you use ctrl-t the indent in the above examples will dissappear,
so if we look closely, you'll see the difference.