This my second attempt with another approach, trying to keep it as small as possible.
I don´t have the time for detailed documentation as I did for my first submission, so just short explanation:

Most of the pattern is repetetive, so I use a subroutine here, called from for loops. as there are only two different lines, I just change the ASCII values before calling the subroutine again. As simple as that.

I wanted to squeeze it into even fewer lines, but commands like "RETURN" (from subroutine) do not work in the same line here, so it has a separate line.

So, in the end you made me going for "small" too. Thank you. ;)