Posting my review in the comments aswell, if that's okay !
After playing this demo for almost an hour, I can safely say that it's a great foundation for a potentially awesome game. The core gameplay has everything you could ask for and it's easy to get lost in the possibilities that it could offer.
The fullscreen mode is a little blurry but I guess it's not final.
The UI is a bit confusing and cluttered but still works fine, I can imagine the challenge when designing such a system.
The controls feel super good most of time except when you have to move fast around the tiles, but maybe that's intended.
Ennemies are fair and diverse enough (for a demo), but their movement is hard to predict so certain spells are less likely to hit, but this part can probably be solved by getting better at the game.
However, attacks that destroy tiles often feel bad for the player because not only it forces them to dodge incoming attacks in a particular way (that's good btw) but also often prevents the player from attacking while dodging, this is clearly the case against the first boss. Destroyed tiles can also trap the player in a 2-tile area with a bouncing attack alternate between them, so it's impossible to dodge. That's unfortunate.
The tile system could also be improved by adding different configurations of tiles in certain battles, but that could actually be hard to integrate without altering the flow of combat.
At the moment, choosing a path over another feels pointless because they're not randomized between each run, and they're not varied enough, but that'll probably change. It's also hard to read where you can and cannot go, there probably needs to be intersections battles/events like in Slay The Spire.
I bring up Slay The Spire because this is the first thing that came to my mind when playing One Step From Eden, the two games are really similar in many instances, mostly the map and the ever-returning deck of cards/spells.
Beyond that, let me say once again that the game has a really strong foundation. It just needs polishing.
Whether it be a more unique art direction (which is kinda good already, just a bit generic), better UI, refreshing gameplay loop, clearer text, controller support.
It also needs content, obviously : More cards, ennemies, bosses, characters, upgrades, decors, events... I have so many ideas ! That's how great the demo is.
So yeah, all in all One Step From Eden is really promising, I hope it goes beyond my expectations, will of course be watching its development from afar, and try it out every time a new demo is playable.
PS : I haven't really paid attention to the music so far, so I don't know what could be improved about it.