A turn based strategy (focused on building a nation/kingdom/empire), that uses card mechanic/s (pure cards or hybrid with other mechanics). Try to not go overboard with complexity, we all know the simpliest ideas are frequently the best

Related topic: http://www.gamedev.net/topic/634578-minimalistic-space-empire-building-game/


Example:
You get 8 cards (just 8 can be displayed at the bottom of the screen quite nicely). You spend resources to play these. After playing ANY number of cards you can end the turn (which means time passes and you get more resources). You do not draw any cards upon end turn through, instead there is an option to "replace a hand" (discard all remaining cards and draw new 8 cards). The replace hand option has a cost which decreases each turn (after 4th turn it's free), the cost is reset each time you use that option. You can replace the hand at most once per turn.

The strategic implication is that you want to play at least some cards in your hand (to pass some turns and make the replace hand cost free) and you can leave some useless cards and "waste them" by replacing the hand before playing these.

There are 2 tricky parts.
1) How to show the "played" cards? In non computer games you have a big table, so it's rarely a problem, but the computer screen is highly limited (and I hate to even think about scrolling). The only solution I thought about so far is divide cards posessed/played into categories (like army, buildings) and display these on separate screens (button to switch between these). Also there would have to be "slots". I'm not thrilled about these solutions through...
2) How to deal with increased resources (and ability to play more cards per turn)? At the beginning you get +1 resource per turn lat's say and a card cost 2 on average. Then you build a factory and get +1 res/turn, then another... You see the problem
It's not that visible with standard mechanics but with cards it's more visible. There are so many cards you can have on hand at once (both display limit and human's brain limit) and increasing it is not a real option...

2) How to deal with increased resources (and ability to play more cards per turn)? At the beginning you get +1 resource per turn lat's say and a card cost 2 on average. Then you build a factory and get +1 res/turn, then another... You see the problem
It's not that visible with standard mechanics but with cards it's more visible. There are so many cards you can have on hand at once (both display limit and human's brain limit) and increasing it is not a real option...

You can use cards as resource in addition to these or have some cards require upkeep. You could increase the amount of required resources. For example, you start with +10, factory gives you +1 and cards require multiple of 20. That lengthen the buildup time, but doesn't make the problem go away.

Go to youtube, search for "Magic: The Gathering Online". Then, go to Kickstarter, search for "CCG" and check out the online ones.

I think there is quite a treasure trove of inspiration to be had from them.

? You really liked the new MTG? I found the interface the most horrible (all this "waiting for the reaction bar to full up whenever there is a chance for an instant interrupt"). To me it was definitely a step down from the old MTG (fully turn based with clicking pass on each interrupt chance). Anyway, I found both not fun interface wise and all that was saving it was the greatness of the MTG itself.

Well, tastes differ, I guesss :D