A few words about the demo itself, you forgot to explain what the red arrow resource is, and it doesn't look like it's even ever used in the tutorial so I'm struggling to guess what it does.
As for the game: the core mechanics are very promising, and it definitely looks like you can build something good upon them. to me it looks like they could work really well as a core for a dominion-style 2p game, where there are, say, 5 target cards to build and whoever builds 3 of them first wins. this way your current game modes can be reimagined as a single player/puzzle mode, and you get "for free" what I think would be an interesting spin on the multiplayer deckbuilder genre.