I am a huge fan of tower defense style games, been playing a ton of Rouge Tower and Bloons TD 6, and while I am super excited at the ideas presented here... this is extremely rough and desperately needs polish.
Cons:
Information: One of the most important things that you need for a tower defense game is clarity of information. You have an elemental chart that means... something. I can't parse it but I'm sure it's very important. It probably has something to do with me playing well until I suddenly lost without warning for seemingly no reason. That or that was the abilities these monsters have that have no explanation as to what they actually do anywhere, there's not even a bestiary or text document breaking them down. I'm not actually sure, as the creatures have no health bars, and there are no damage numbers, so I don't know how much damage my towers were doing outside of "enough", until they suddenly and completely were no longer doing that. Of course, it may have had something to do with my tower placements, I'm not sure, as the towers also aggressively obscure their information. They don't even have range indicators on them even after being placed, let alone before. As a result, I don't know if the upgrade cards I use on them are worth anything. How useful is +2 range on a tower with a range of ??? Does that cover the whole map, or is it a fraction of a fraction of an inch? I have no way to find out besides careful observation, where a simple indicator circle or square would demystify it. Everything is so deep in layers of obfuscation that even basic functionality is a complete mystery. Which is only made all the more aggravating by the presence of...
Elements: Elemental strengths and immunities are fine. In moderation, that is, and when you have several ways to play around them. to this, I point to Bloons, which has enemies immune to certain damage types, but there are both many other damage types, the ability to upgrade towers into different damage types if needed, and several support towers that can let others entirely ignore said immunities. Rouge Tower has different health types that are stronger against two damage types, but weaker against one of them, but all the tower types can do valid damage to them either by bumping up the relevant kind of damage or just through raw numbers/good placement. Now, see above where I said I don't know how much the towers I was using and their respective elements were responsible for my sudden losses due to lack of information, but if you're focusing more on damage immunity than damage multipliers on that chart, that is just going to be deeply frustrating if there isn't an accessible way to work around it. Your tower effects are very cool and good at dealing with a wide variety of threats, but if a swarm of water immune ghosts just breeze through my defenses, or you throw a bunch of enemies at me that can only be damaged by fire, the slowest shooting tower in the game, then if I have built anything other than for specifically dealing with them, I lose right then and there. And then, even if I have, any other enemy combo that aren't what I solely built around will insta-wipe me. This potentiality combined with me not being able to tell if that's even what's happening or not leads to prompt frustration. Which isn't helped by...
Wow. That's rude: So I went from being able to effortlessly wipe out every enemy as they leave the gate to not being able to kill a single enemy in the wave for... some reason. I've lost. Bummer. What doesn't help is when you tell me "You've fallen after defeating a PALTRY 200 enemies, how pathetic. You got a PITIFUL 20 orbs, not even enough to be able to get this new card! Oh well, sucks to suck!" My dude. That game over screen took me from "Hm, this is rough, but I'll keep trying." to "Oh frell you and frell this game." Mocking the player for failure is a bold choice in and of itself, to do so in a game genre that lives or dies on being able to figure out what's happening and why you lost so you can adapt your strategy after, as you hide almost all of said critical information, it doesn't spread good vibes, to say the very least. Makes me far less likely to extend your game any benefit of the doubt, since you seem to find my efforts so hilariously pathetic.
Pros:
Neat Towers: I really like the lingering damage zones the water towers make, that combined with the grenade-launcher style bouncing earth bombs makes shutting down choke points especially satisfying, even more so when I can add little combos here and there like adding a slow to the AoE's and the like. Fire doesn't have enough punch or do enough damage (it feels, at least) to really justify itself, and the "INSANE" fire rate of the wind tower feels more like "Very slightly faster than any other tower, probably." Except at times it seemed slower than the unupgraded electric and even earth/water towers? Still, you have some interesting ideas with the elemental towers.
Enemy Design: They look neat, some of them are pretty cool, and they all manage to keep to a generally "Could be from the same universe" vibe.
That's about all I really have right now for the positives, I'm afraid. You already know about the other things in dire need of assessing. The UI needing updated, card art being unrepresentative. The desire for more towers, maps, cards that impact the game a bit more. A need to build maybe certain decks for certain map-based situations rather than just being able to make one deck that is "strong enough", difficulty being way out of wack (Again, your game seems to think I'm pretty gosh darn pathetic for loosing on very easy consistently by wave 10 or so, rather than it being something where maybe your difficulty isn't actually good.) I recognize that game development is hard, but as someone who has played this game hoping for an exciting new twist to both deck building and tower defense, I recognize it needs a great deal of work to actually be something I would ever want to revisit.