Artillery Overload is applied to the player that buys excess artillery - it has nothing to do with what the other player does.
Both could overload and thus pay penalty points to
each other.
(cannot be bothered looking at the exact numbers in the code - it should be in the Game Guide in any case)
If you are an assaulter - you can buy as much as you like, no limits
If you are attacking (advancing) - its something like 25% limit
If you are in a meeting engagement, its something like 20%
If you are delaying or defending, its lower still
Should you go over the limit, a
fraction of your overspend is given to the other side as artillery overload points.
When purchasing - the artillery %age is displayed, and changes colour if you are overloaded.
Some folk are a bit OCD and worry if they have say 50 points of overload charged to them - that is nothing in a game of thousands of points. 1000 points may be worrisome though. But it is up to you to decide if giving the other side a few hundred points is worth the extra batteries (i.e. you bet that you will do more damage than you gave away).
Now in the
next version of the game the artillery overload will not be applied to
scenarios, since the scenario designer "knows" what the force balance should be. So the scenario would be the sort of thing where you have 2 SF teams and 27 batteries of supporting 175mm off-map sort of thing. Suhir made a valid suggestion regarding scenarios, and I will be running with that.
Arty overload is deliberately there to guard against the sort of player you might meet in a PBEM who has 2 observers and some scout cars on table, and 72 batteries of SMERCH launchers with cluster bombs off-map. (Exactly the situation I recall happening in the 1970s in a National 1/300 WW2 tabletop competition before army lists. One guy bought enough FOOs, and the rest of the points spent on off-map batteries. That's why army lists came in the next and subsequent years!.)
Then there was the Warhammer army that consisted of precisely 1
invisible dragon - now that one was cheap to buy and very easy to paint