My opinion/experience on each card (yea coz im wordy like that):
negative stone: i was perplexed it would break the balance, but i guess it's pretty interesting; you basically have a free very expensive card to play, but you have to play it last and you can't keep your hand (so it's useless on 67-stone Draw 2). I would usually use it early on with -98 or -61, but i think it worked very well with 77-Surround Immune lol.
1-stone: basic, very useful early, sometimes you want to keep some depending on your max energy. (Like against the guy that turn your deck into 37-stone and you had like 40 energy, my deck was just 1-stones). Being able to place a stone is always good.
2-burn: useful in early game. I'm not sure getting a +1 burn for twice the price is worth.
3-cycle: wasn't useful in early game, but late game I think it becomes a very good card so you can search for a Draw 2 when you need one, or discard a Negative stone when you don't need it. It's pretty cheap so it can just replace the 1-stone when you have enough energy. I tested 9-stone, but 3-stone seemed to work well enough, 27 doesn't seem worth it though.
5-freeze: really good early game, i'd say much better than burn lol, the 5-primeMaster was quite hard early on. It's kinda funny how early in the game, it's important to remember to use your most expensive cards if you can, and keep your 1-stone in hand so you can play them next turn.
7-immune: good thought that you limited the numbers of stone we had available lol. Otherwise fighting primeMaster 19 would have been much easier. Good stone throughout, it's really what allows you to set in stone something, though I kinda just used -77 late game.
11-surround: MVP lol, I think even early it's quite nice (i tried to unfreeze it with 49-stone, quite fun). It's really useful when you need to quickly gain space and there's a limited amount of turn (like against primeMaster 97). Late game it becomes quite cheap too.
13-bewitch: i was really confused what it did at first, took me quite a few games to actually understand how it worked. It depends on the opponent we're fighting, i think it's mandatory against those last fights where the Prime Master has 300 Energy.
17-diagonal movement: kinda funny, I think I used it for some specific maps, but in the end the 23-stone might be better in general?
19-destroy all surrounding: oh lord when you get this, it's when the stones get really insane. This has nice chemistry with 7-immune, I had some fun trying to destroy everything and putting 7-stones in the empty spaces. Really cool stone and not that much worse than 31-stone or 61.
23-jump: I didn't really it much, but when i started using it late game it was really good, you can really rush down and take a lot of space with 11-stone.
29-stays in hand: mhh didn't use it at all lol, i don't think it's very good? Kinda expensive?
31-remove stone: very fun like 19-stone, but also has a slightly different use case (19-stone can destroy up to 3 enemy stones, 31 always destroy 1 enemy stone but anywhere). So 31-stone doesnt need the 7-stone to work well, but it's quite more expensive.
37-copy: kind of a gimmick lol? I don't think it's very useable either.
41-reverse colors: very weird, didn't use it, don't know how to use it well. But it does beat Immune.
43-next card is free: was always kinda too expensive to be useable? And when you could start using it, you have minus stones for expensive cards instead. Also it's very conditional, it can often become a dead card in hand.
47-discard: it's really just an AI-card, I don't think players will really deckbuild with that.
53-time: looks fun but i didn't use it much. seems too expensive.
59-remove from deck: oh lord, very bold to include this card. You basically have to make sure any 3 card combinaison doesn't insta-win the game. I might have used it a few times to get 61, -61 and 43 in hand or something lol.
61-cover other: very cool idea again, it's highly dependent on turn count. I felt sometimes it was too slow/not worth,
67-draw2: the long awaited draw2 card lol, man that primeMaste 67 was insane. Really cool card, very useful even this late.
71-factor: i didnt understand at first. It's very situational? The only use case I found was using it with a 81 (4 * 3-stone cards) to get a really early lead, but even then it's luck dependant. Most of the time you would it, you just get trash in the deck.
79-surround stone: was okay, i used it a bit, but then just used 77 instead lol.
83 to 97: didnt use them lol, 89 is just a card for AI. 97 comes too late (and i guess it's too expensive). 83 might have some potential but didnt test.
X stone: maybe useable, but doesn't seem that good (too random).
Repeat the last card: i think it's a bad card.
Calculator: best card in the game obviously, but actually it's not by too much. I like how the value stays the same throughout a game. It's a nice gameplay balance, you get to choose immediately any card (good short-term) but it might unbalances your deck composition long-term.