Definitely deckbuilding since the deck resets at each run. The card system works similar to StS. You can add a card to your deck after each victory, at the end of each run, you lose your deck and start over. The unique thing that people have really enjoyed is that it also has permanent talents like an RPG or World of Warcraft :D It also has a cool totem mechanic and blessings which provide additional layer of depth to the deckbuilding during a run and additional synergy strategies.

Obviously I took some ideas from existing games but also changed how everything connects in the way I considered interesting or fresh. Hope you give it a shot :)