[Icehouse] Martian Coasters Question - Seeking Other's Thoughts

[Jeff Zeitlin]

On the wiki, M5rammy asks for clarification/others' interpretation of
the rules pertaining to digging, and offers three interpretations:

(1) You may choose to dig on any turn.  It costs (pipsize) movement
points PER LAYER that you choose to dig upward.  If you roll DIG, you
can dig ALL of your pieces at no movement cost.

(2) You may choose to dig on any turn.  It costs (pipsize) movement
points to dig to the top of the stack, regardless of how many layers you
are digging upward.  If you roll DIG, you can dig ALL of your pieces at
no movement cost.

(3) You may dig only if you roll DIG.  When you do, it costs (pipsize)
movement points to dig to the top of the stack.

He/she also inquires if there is an option to dig only partway, if (2)
or (3) is the preferred interpretation.

My reply was that I believe that interpretation (2) was the correct
interpretation, and that since I could not see a reason why one would
want to dig only partway up, I would disallow that option.

Discuss?