Is acp-min useful?

[Stan Shebs <shebs at shebs dot cnchost dot com>]

Recently Keir Novik was asking me about a change to the behavior
of acp-min that happened a couple months ago.  Actually, what I
had done was to make the code work just as the manual described,
but in practice it seems less useful that way, which suggests
that we should finish doing the thinking that I skipped over
when adding acp-min.

OK, now that everybody has referred back to the manual to see
what acp-min is supposed to do, the original theory was that
I thought there ought to be a way for acp not to be quite so
tightly tied to turns.  So one could have a game where units
rest for a couple turns and thereby accumulate extra acp (up
to acp-max), and/or could expend more acp at a critical moment
and go into debt, down to acp-min, then rest until acp went
positive again.

However, for a long time the code did not let you do any more
action once the acp went negative, even if you were still 10 acp
above the min and moves only cost 1 apiece.  Only the last action
you did could use up the acp between 0 and acp-min  The fix I did was
to let units keep doing actions all the way to acp-min, and only be
immobilized during the next turn, if they hadn't gotten enough
acp-per-turn to get acp back above zero.

The motivation for all this was panzer.g, which was designed to
allow tanks to be "on a roll" and get double movement in a turn
if the player prepared for it.  But that's not what happens.
Instead, on the first turn players casually use up every available
action point, so that everything gets its double movement then,
and then acp just ranges from acp-min up to 1, instead of the
usual 0 up to acp-per-turn.  The problem is that the interface
doesn't provide any way to say "stop moving at acp 0, unless I
say to keep going".  However, even if interfaces got such an
addition, it seems like it would make playing unnecessarily
difficult - players would have to be doing their calculations
on negative numbers when deciding how far into acp debt to go,
which is a bit much for a tactical game.  It also looks like
other games have consistently avoided negative allowances.

So here are the options I see:

1. Leave kernel alone, add to interfaces (somehow) to give
finer control over acp usage.

2. Eliminate acp-min entirely.  Use free-acp to handle actions
that might need more than the remaining acp.

3. Revert to the pre-fix behavior, where acp can go negative,
but negative acp ends the turn for that unit.

I slightly favor 2. over 3., because GDL already has too much
obscure stuff, but I could go for 1. if somebody came up with
workable interface mods.

What do you think?

Stan