Collectible Card Game Headquarters

I know it's something simple I'm doing wrong but I'm stumped as to how to do it properly.

When wanting to use an repeatable activated ability on a card, as an example Armor of Faith, I double click the card to use it and as a result all of my plains become tapped. What should I do to not have my mana pool filled with all usable mana for that card?

This seems to be a bug : instead of charging you of a single W for a single activation, the card charge you with an X cost payable only with white mana.

This is not a bug, it's the way the game has always worked!

Do not double click the card if you don't want to use all of the mana that is available to be used by a card like this. For example, if I have a Looming Shade on the table and I want to only use 3 of the 5 untapped Swamp I have available, I click one time on the Shade and then pay the cost with one mana by clicking on a Swamp and I do this for each 1/1 I want to increase it's power to. If I want to use all the Swamp available to pump it up at one time, then i would double click the shade to have it tap all the Swamp at once.

I see now, it'a an issue linked to the old rules. It's a bug under current rules : a single activation costs you only 1 mana of the required type, not X mana.

It has nothing to do with the rules, but in the way the User Interphase was designed when the game was built. Double clicking was simply a faster way to tap all the pertinent mana at once to make it easier for a player to do so instead of having to click on one land after another if a player wanted to use all the land at one time.

Thanks Bog Wraith, I knew it was something silly like that.