Co-op defending mechanic

As much as I tend to dislike blind bidding, maybe something like that would work as a group effort defense.

Say that it takes a certain amount of resources to defeat an enemy. During some kind of "defense round" each player secretly bids a number of resources. If the total is enough resources to defeat the enemy it's gone - otheriwse it keeps going. Might be nice if everyone loses their resources regardless of the outcome. Could put a little more tension in the bidding process.

Now that I wrote that, it seems vaguely familar. Hmmm... is something like that already used in some game? So hard to tell after awhile where ideas come from - you know.

Yes, it's used in A Game of Thrones where all players defend against a Wildling Attack by blind-bidding. If the sum of all bids is equal to or greater than the Wildling Threat Level, then the players all win; otherwise they all lose, and all suffer damage. In either case, all players lose what they bid. The player who bid the least in a loss takes extra damage; the player who bid most in a win gets a bonus. There's a separate tie-breaking mechanism for awarding the extra damage/bonus.

IMHO this is a great mechanic. The resources you bid with are useful for several other things, and wilding attacks are unpredictable. You must keep some resource in reserve against a sudden attack, and when you bid you must worry about whether your bid will be lowest in the event of a loss.

Amun-Re has a similar blind bidding process, although the total group bid doesn't defeat a common enemy, but is used to determine the temple level, which determines the income from farmers and camels.

Bruno Faidutt's Terra also features a similar process, you all have to play a numbered card which are added up to save the world from something terrible, although that's not a blind bidding process, but a once-around-the-table action.

Zzzzz,

Cities and Knights of Catan use this kind of cooperation. I'm currently working on a variation of Republic of Rome.

The concept is that Senator in Rome buy army/fleet to send against wars and event. It is a very good historical game, but it is very complex. You can try to backstab other player for your personnal gain, but you have many chance of failiure.
1 - Rome Senate goes bankrupt.
2 - The population revolt due to war desaster and bad management. (To balance this you have Bread and Games)
3 - Rome face more than 3 wars and collapse.

Winning isn't that easy because the losing condition are always present. Mostly wars and civil revolt. Condition are you have a lot of influence. (Gain by occupying prestigious position at the senate or by winning wars)
Or being rebel leader in a highly unstable republic.

So in short the game is based on the cooperative play. I find it fun, but too hard for normal players. That is why I'm trying to get a scale down version without Senate and easier gameplay based on the Napoleonic Wars.

Have a good day.