Here is what I would call a BASE CASE of spam. This is designed to be clear cut, while in game it would rarely be this obvious. However, we have to try and start somewhere.
If a player sends minimum population attacks, that are designed to be as small as possible (ex. 1-10 slingers per attack). If these attacks are constant over a long period of time (several hours with little to no respite), and more frequent than tactically necessary (like locking out golding of troops in the target city), then that could be considered spam. The period of time, frequency of attacks during that time, and impact of the attacks are all what makes this case clearly spam. It is designed not as a tactic to take or clear a city first, but a tactic to directly influence/pressure the player themselves. The tactical nature of the attacks becomes voided by the lack impact the attack has. Keeping a city with lots of unused population specifically for this purpose is an obvious indicator that the intent of the attacks is to spam.
The exceptions, which would NOT be considered spam;
Breaking up a myth nuke to clear militia and farm favor in small groups to avoid zues rage. These attacks could be more frequent than the golding lock out, and could even be done over an extended period, but if the attacks stop when there is no more favor or resources to loot, this is fair play. If the attacks rotate cities of the same player, this is not necessarily spam, you are checking/looting multiple towns, trying to catch returning or dodged troops, etc. The impact of these attacks is measurable and has clear tactical/game value; looting favor and resources, and BP hunting.
I agree with what you've said about fairplay.
About
defining spam subjectively, I'm not so sure - I feel like the playerbase is already divided on this before you even begin the base case.
The word 'spam' is used by a lot of players loosely for a wide variety of things, and I think it's necessary to distinguish between '
acceptable' and '
unacceptable' spam. It sounds like this is just a matter of semantics (we could just call everything that's unacceptable 'not spam'), but there are players, including myself, who feel not all forms of spam are unacceptable (while they would still be called 'spam' by most).
Eg. mass HCing 50 of the target's cities or sending 500 x 1k spies across all their cities. I would casually refer to these as 'spamming', but I don't think these are unacceptable (although even then, some feel they are not). If someone gets 10+ attacks at once, they often will say they are 'being spammed'. If someone attacks me a lot of times during the day, I would call them 'spammy'. But that doesn't necessarily mean that we think their actions are unacceptable - hence I think it would be best for us to distinguish spam in this way.
Now, about what
is and isn't acceptable spam - I think even then it is very hard to distinguish a '
base case' which a vast majority can agree on without going to extremes. I feel the middle area between acceptable and unacceptable would be too large, rendering a base case pointless (which once again, would leave deciding what is/isn't acceptable to the moderator's discretion in most cases).
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For example, in your base case you imply that
tactical necessity (and so, the player's
intent) is important in deciding if the spam is acceptable or not. I disagree - it would mean the exact same actions conducted by different players could be judged differently based on their intent. It is not so much the ideal of this rule I disagree with - it is the practical implications it has. It would mean players can get away with what is 'unacceptable spam' (by your definition of tactical necessity) by lying about their intent behind the spam. Players challenged by moderators would seek to invent 'acceptable' explanations for their behaviour.
You also imply intending to
primarily pressure a player is unacceptable. But the main aim of aggressive gameplay IS to pressure your opponents to give up (yes,
make them go into VM; yes,
make them quit). If your opponents give up, that means easy cities for you which gives you a clear tactical advantage. For me, this is an acceptable strategy - I think it is a part of the game, while I understand that others would consider this attitude to be lacking in sportsmanship and unacceptable. Now, even if one of the forms of 'unacceptable spam' is to make others quit the game, no one will own up for it - players will say they were attacking for some other reason. This leads us back to the original problem of leaving the jurisdiction of individual cases in the moderators' hands.
You mention '
Keeping a city with lots of unused population specifically for this purpose is an obvious indicator that the intent of the attacks is to spam'. I agree that it could be, but there are other reasons/benefits for keeping a mostly empty city. Rather than spam, the city can be intended to just conduct innocent HCs on the enemy (I commonly do this for newly taken cities on red islands). The player might not have decided yet what to build in that city + keep their options open, or maybe they're using their resources for other cities. In the end, this leads me back to my point on
intent - it is hard to judge whether or not a player's intent is acceptable when they can lie about it whenever it is not. And about the point itself, I personally find this tactic to be completely ok, even if the player IS intending to spam with the city. The action is balanced - if you're keeping a city empty, then that's one less nuke you could be using. If my opponents do this to me to spam, I'd feel they're the ones who are losing out.
Onto what you say
is acceptable - again, I feel that players can use some of these reasons to try justifying their unacceptable spam and get away with it in some cases (eg. 'If the attacks rotate cities of the same player, this is not necessarily spam, you are checking/looting multiple towns, trying to catch returning or dodged troops, etc.').
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These are my thoughts on trying to enforce spam as a
subjective rule - I don't think it's possible to be fair about it. (Yes, I was complaining about a lack of guidelines in the OP, but I'm also saying that I don't think they would be enough to solve the issue - I feel we need hard limitations on spam, preferably coded into the game.)
With rules like player harassment, which don't actually relate to the game itself, it is possible. There is no tactical reason players need to come even close to breaking such rules. But there clearly is tactical value in conducting spam, and so players will always look to push the boundary of 'acceptable' as far as possible without breaking the rules. The players who can push it the furthest without being penalised by moderators gain an edge over their opponents.