at the risk of being the shill but i think its helpful and what you are looking for, https://untap.in/ does this, solo play both mirror play your deck AND deck vs deck where you play 2 decks as one player, alternating turns.
I always wanted https://untap.in/
(yeah, I built it) to feel like this... free-form, chill, a bit messy. Just moving cards around, making mistakes, fixing them together, like a real board game night.
But after 10 years of user feedback, it ended up somewhere else.
Still nice seeing someone else land closer to that original idea. Well done.
Interesting, this one did pop up on my radar a while back, i always keep my pulse on the playtester space :) Although cardtavern one strays away more from the free form play that simulates a kitchen table game of magic, piles and structured zones ect, much like untap.in has (as i mentioned, users want fast structured play and QOL mechanics built in). The ops vision seems to be its a table with some hide/reveal and shuffle mechanics, do what you want after that. Which i appreciate, allows a bit of fun.
At the risk of being another shameless plug this is a subject i've dedicated a good chunk of time to over the last 4 years in a project to simulate mechanics of CCG / TCG card games. The goal is to give the user only what a table and paper game would provide. https://untap.in
It's all in browser, supports up to 6 player multiplayer card games, BYO cards (user uploads card images). YES you can spectate games if you want to have a look.
This has been a growing industry, i have noticed in the last 4 years people like the idea of being in control of their game, playing on the mistakes their opponents make and having the skill to think about the game with out the computer doing the work for you like in most digital card/boardgames from today.
Untap.in is a personal project, has about 100k registered users and 1600 daily active, its a big community. All of this is being serviced by a sole dev (myself) in my free time. The likes of these frameworks should make it extremely easy to get board games through prototype and playable, its a great thing.
