Spellweaver is a CCG that, while not at all a game I recommend, I'll always remember, because of what it taught me about game design, and about myself. (Disclaimer: I last played several years ago, so this may not be entirely accurate.)
The game is inspired by MtG (and the lead creator is a seasoned MtG expert), so the rules are based on MtG with a few changes, most of which are massive improvements:
Creatures can attack each other, so that the defender doesn't have an enormous advantage that encourages players to sit around piling up a dozen creatures on each side and never attack. The speed stat is added to creatures to determine what can attack and block what; and that alone adds so much strategic depth and design space.
They even mostly fixed the mana screw problem! It's a bit of a clunky mechanic in that it kind of makes you wonder why Shrines are even still a thing instead of using Hearthstone's mana system, but basically you can exchange any card in your hand once a turn for something like an 85% chance to get a Shrine.
Still, the game is killed by the same thing as MtG: no concept of a power curve. Many cards are so efficient and lacking in drawbacks that every deck with the right colors wants four copies of them period, and many more are just completely useless. In fact, if you divided the range of strength that the cards span into three equal sections, I think less than half of them would be in the middle! And the devs know that. They don't care because they think the only thing that matters is having a diverse meta. They don't understand that individual card balance matters for reducing draw RNG and obvious choices in deckbuilding.
Funnily enough, toward the end of my era, almost everyone I argued with on the forums agreed that the game had a huge balance problem, but nobody could agree on which cards were the overpowered ones. The forums were also a ridiculous cesspool of toxicity.
Before I go on to the moral lesson I learned, I want to mention a few more gameplay criticisms. The next one is the problem of creature size: most of the removal (cards that destroy enemy creatures) is geared toward dealing with a few big creatures rather than a swarm of little ones. This meant big creatures often had to be obscenely overstatted to see play, which they were, and some aspects (Nature/green and Wisdom/blue) were almost completely lacking in removal, so they had other broken auto-includes to compensate.
There were also a few cards seemingly designed without any thought of how they would affect gameplay, like Guardian of the Faithful and Voidtouched Subordinate, both of which made it very difficult for your opponent to profitably attack you, leading to a lot of miserable stalemates. Electrostatic Storm was a persistent spell that killed your own creatures as much as the enemy's, so it's only use was in "One Turn Heal" decks which played no creatures, but packed obscene amounts of removal and used healing spells to win by life. Almost everyone hated OTH.
We also have to talk about Cataclysm... the card that destroys all creatures. This card taught me what a horrible mechanic that is in a CCG. And I will never forget the days of "Vamp-Lamp", a deck that used Cataclysm and a creature called Lamp of Zapphir that was immune to it.
Oh, and let's not even talk about the insane nudity rate on cards depicting female beings. It's just shameful. (And yes, I do now consider the game immoral for that reason.)
I guess that's enough ranting about how horrible the game was. I still have to give the developers some credit for coming up with a massive improvement over MtG.
A story I want to tell is my attempt to create my own CCG inspired by Spellweaver, by reducing RNG, increasing skill and greatly improving card balance. My CCG died in the playtesting phase. The reason was that although I came up with some cool mechanics and succeeded in reducing the draw RNG, I think I inadvertently took almost all of the skill out of the game by making hands public information. I didn't realize how much of the skill in Spellweaver was in weighing risk and deciding whether it was worth playing around a card that your opponent might have. Without that, there were virtually no non-obvious decisions in-match.
But also, the dissatisfaction of playing my own CCG taught me something else: the problem with RNG is not that Spellweaver had too much of it. The problem is that Spellweaver had it. No competitive game should have it. I might have been able to make my CCG better than Spellweaver, but I could never make it anything more than a joke compared to Prismata or Go. So I scrapped it.
The last thing I want to talk about is the lesson it taught me about myself. More specifically, about self-deception. I witnessed two forms of it in the community. Most other people did it by convincing themselves that the game was fair, that it was not bullshit when they lost to whatever grossly overpowered card because they didn't draw their equally overpowered counter in time.
I, on the other hand, convinced myself that it was bullshit, but that I was having fun anyway. Then I had a streak of some twenty games in a row against a deck that was essentially the descendant of Vamp-Lamp after Lamp and other supporting cards got nerfed and new ones were introduced to take their place. Finally, I examined my recent memory and came to terms with that I was no longer enjoying Spellweaver, and I quit.
I kept telling myself it would get better with the next balance patch, and I think I really did believe that. I think another part of it is that I was afraid of what I would feel if I left Spellweaver, though I'm not entirely sure why. What's for sure is that from that day on, I learned to be more skeptical of my feelings, and realize that self-deception is a very real thing that even rational people do.