Done as a short design exercise, Harmagix is 1v1 deck-building game where players use a shared resources pool as both currency for purchasing their cards *and* the medium for attacking their opponent. It currently exists as a paper prototype which can be downloaded here: http://ryanburrell.com/dev/harmagix.zip
After the few days spent on it, Harmagix ended up in an promising location. The gameplay is definitely strategic and the core of the unique gamble involved in purchasing a card works. Of course it all needs some tuning, and the devil is in the details of the cards themselves and the various mechanics they allow. I iterated on this a few times to get the gameplay into a place where there are a number of viable strategies for victory and the actions of the cards feel interesting and rewarding.
Given more time, cards would ideally be themed to reinforce effect or play styles within an element – earth cards would deal more with damage protection or health retrieval, air would provide more card movement (drawing, discards), etc. I’d also like to somehow work in a like-card triggering mechanic that encourages players to stack their deck with cards from the same element, much like Star Realms or Ascension. For instance, playing two flame cards could cause the opposing player to burn, slowly drawing water toward them for a certain number of turns.
The game could easily be made into an actual physical product or converted into the digital space. Harmagix is by no means perfect, but as my first attempt at creating a deck-building game I count its outcome and what I learned from it as a great success.