indentation mode of custom file format

indentation mode of custom file format

[Luis Kornblueh]

Hello,

I need some help. I have no idea on how to program in Lisp. I managed to 
get a highlighting
mode working for an simple file format as derived mode of sh-mode, but 
do not manage at all
to get an indentation mode. The file format looks like:

# comments
text
text
[level1]
     text
     text
     [[level2]]
         text
         [[[level3]]]
             text
              # comment
     [[level2]]
     text
[level1]
     text
{% comment %}
     [[level2]]
         text """
             text
             text
         """
         [[[level3]]]
             text

and should be indented with spaces as shown. It would be great, if 
someone could help me.
I found plenty of examples with opening/closing structures, but none, 
with such an format.

Thanks a lot,
Luis