Following the release of Shiny Chariot TCG, feedback I had received and my own griefs with the project led me to consider a second, different version. Consigned here are, for the time being, only thoughts and ideas on the what, why and how of this different version. Whether I will manage to bring it to fruition is a different matter entirely.

Still thinking about the Shiny Chariot cards, and how the version I proposed fills the original purpose of making the game playable based on how it was presented in the show, but how it didn't exactly constitute a proper Little Witch Academia card game
So here I am noting down my thoughts once more. As I've mentioned when I released the previous version, my biggest dissatisfaction lies with the fact that the game, as it is, has little to do with the story of Little Witch Academia in a thematic sense. My first intinct was to make the search for the Seven Words the win condition of the game. One way to make that viable would be to have each word unlocked after a specific amount of counters is hit. (Could be, for example, nine counters, to mirror the Nine Olde Witches and the Grand Triskellion in the lore, nine being a trinity of trinities. On that note, starting with hands of three cards drawn randomly could allow to keep the small deck size necessary to offer variety given the small number of total cards available. If I want to be cute about it, I could go fifteen to twenty-one cards, both multiples of three.)
For the cards themselves, we could step away from the strict colour identity comparison, based on Magic the Gathering, and consider them as alignments, opening up the possibility for sub-alignments, something somewhat similar in spirit to Yu-Gi-Oh: Forbidden Memories.

The possible alignments could be something like this:
Sun cards: Clear Sun / Eclipse
Moon cards: Full Moon / New Moon / Waxing / Waning
Star cards: Ursa Major / Southern Cross / yet to be decided constellations (I'm thinking either three or five in total)
For now, I'm considering the possibility of having those sub-alignements chosen at the start of the duel, which would allow for more flexiblity in deck building (the same card potentially serving different purposes depending on the sub-alignment chosen.)
As for the main play mechanic, the meat and potatoes of the game so to speak, I doubt a MtG/Yu-Gi-Oh clone would fare well with hands of only three cards. Instead, the game could be about building a board, ramping up to arranging cards with one another in a way that allows them to synergise well, potentially striking a balance between cards that stay on the board after being played and cards that are returned to the deck and have to be drawn again.

As a quick addendum: If this were to be made into a single-player video game, funnily enough, lifting that one scene from the show where Akko shows the game to Lotte and Sucy could be a decent way to make a tutorial, having Akko explain the mechanics of the game in a sort of tutorial duel, explaining her moves to the other characters in canon while having the player making those moves alongside her. That would be for the basic mechanics at least, what the win condition is, what the stats do, that kind of stuff. For the sub-alignments, I think it could be interesting to have that happen after the player has had the chance to have two or three duels to get a good feel for the basics, and then having a character introduce the notion, teaching that specific idea to the player while at the same time making it clear Akko, and through her the player, has room to improve over the course of the deck. This is mostly a stray thought for now but Diana could very well work in that role, dueling with a deck that Akko just beat, but managing to keep her on her toes by playing that same deck with a different alignement which is a lot more effective given the way the deck is built. Her sharp analytical and quick thinking would suit this kind of stunt, while hinting at her own past fondness for the cards (hence her having a level of familiarity with more specific mechanics), all the while keeping her role as Akko's rival

Some more thoughts on this:
In order to combat the small hand size, and while still keeping the relatively slow pace a three card hand would impose, each player draws two cards at the beginning of their turn. The player taking the very first turn only draws one card on this first turn.
The sub-alignment idea is not the greatest, as it would be a steep learning curve, even if the game was digital in which case there could be dedicated ways to keep track of the sub-alignments, which is to say nothing of wanting to potentially play the game physically.
Instead, I'm thinking of potentially having a Celestial Guidance card. Essentially, the idea would be that, at the start of your turn (mandatory on turn 1), you can set one card from your hand as your Celestial guidance. By using card as cost, they generate Mana equal to their own Mana Value (the number of moons, suns or starts in the bottom left of the cards) of the colour of you Celestial Guidance's Mana Identity (If it's a sun, moon or star card).
Taking the cards Pegasus and Fountain of Polaris cards as example, the situation is as follows: Pegasus is set as my Celestial Guidance, and I use Fountain of Polaris as Mana cost. Fountain of Polaris' Mana cost, as indicated in the lower left, is 4, and Pegasus, as indicated above the card art, is a Sun card. Hence, using Fountain of Polaris for cost would generate 4 Sun mana.
Celestial Guidance cards could be discarded and replaced with another at the beginning of each turn, in order to not lock decks into a single colour identity. Ideally, some cards would have effects which interact with being the Celestial Guidance card, in order to not make it feel like a dead card you don't really get to play.
Another point I'm considering is the number at the bottom right of the cards. While I originally interpreted them as Attack and Life values (a very Magic the Gathering way to look at it), this doesn't make much sense in a system not about direct with another player. It could be interesting to have those values represent different 'states of being' for the cards. This would make each card, essentially, two cards in one, with one version being the regular state and the other being the Eclipse state (to keep with the celestial bodies flavour.) The left number would be a value in the regular state, and the right would be a value in the Eclipse state. (Which value that is, I'm not entirely certain yet.) Cards would also have different effects in regular and Eclipse state.

This still leaves me with yet unsolved problems, amongst them Mana cost. In the absence of other ways to generate Mana, I have defaulted to using the cards as a way to pay for costs. This would cause an issue, I think, as even with a way to recycle discarded cards, (which I will inevitably have to work into this version again to combat the small deck sizes,) having a bunch of cards in your deck meant as, essentially, discard fodder, isn't very fun. Which means I should either design the discard system around the fact that discarded cards need to factor into a player's game plan and be part of their strategy, or come up with another way to generate mana to pay for cost.
The other big problem, as it stands, is interactivity. As it stands, the game would be mostly just two people doing their own stuff, on their own turn, with no interactivity between them. I need to come up with ways for the players to have opportunities to disrupt or counter the other player's moves.
One idea I considered would be to make Shiny Chariot TCG and asymetrical card game. My point of reference was specfically Genius Invokation TCG, the Genshin Impact card game. In the in-game version, many duels are challenges featuring the game's monsters and environments, mirroring the broader situation of characters fighting monsters in the wild. This, however, would mean having to use the cards again, in a dedicated alternate version with their own effects and rules, and asking players to build not one but two decks at minimum to play. While it's not something I want to dismiss outright, I feel like this could risk making the game feel cluttered and bloated, for lack of a better word, not to mention making the learning curve even steeper.

More notes on this matter.

Here's a quick mock-up of what the playing field could look like. Note the moon wheel at the center, consisting of three moons: One waxing, one full, and one waning. These are the three zones for cards in play.
One idea I think is worth keeping is the 'Celestial Guidance'. The card set on the full moon offers Celestial Guidance to the others. In order to summon cards to the waxing and waning moons, mana of the same colour as the celestial guidance must be paid.
Ideally, the idea of cards having two effects would remain. One for being set on the full moon, and one for being set on the waning *or* waxing moon. (At least for most cards, I am not entirely excluding a card or two having three effects in total if I feel it is warranted.) Note that a card does not have to possess the corresponding effect to be played in either position, it would simply be less useful than in another scenario.
It is worth noting that, if a card is too powerful, it could be interesting to have a negative waxing/waning effect for balance's sake.
For the card scores, I believe this also unlocks what exactly to do with them. The left number would be the waxing score, and the right one the waning score. Going back to the Pegasus card poster further up, its waxing would be 2, and its waning 3, mirroring the position of the cards on the mat relative to the full moon at the center.
If I do end up keeping the idea of some sort of combat phase, this could allow for more strategic play, I believe. The idea is this: Cards in waxing and waning contribute to the full moon card's stat with their own. If I have Pegasus set as my full moon, and Fountain of Polaris as waning moon, then Fountain of Polaris' waning is 5, Pegasus would get a waning of 3 plus 5 totaling 8. During a hypothetical combat phase, the player taking their turn could chose to do battle using one or the other stats, and the opposing player would have to try and weather the battle with the opposite score. (I.e. if a player chooses to attack with their card's waxing, the opposite player must use the waning of their own card.)
Regarding interactivity and the discard issue, beyond the idea of recycling the discard into the deck once the deck has run out, which I might keep, there might be an interest in some cards, in lieu of their traditional full moon/waxing/waning effect, have a discard effect, being a trigger effect that you can activate form the discard in response to things happening on the field.
From there, the idea would be to accumulate Revelations to discover one of the Seven Words of Arcturus. Revelations would be represented by the Shiny Rod on the side, each of its gem becoming illuminated (or marked by a token) as Revelations are gained. (Revelations are essentially victory points, of which seven in total are necessary to win a match.)
For the time being, I think that a victory point could be earned if, at the beginning of your turn, before you draw, there is still a card set as your full moon. Though this idea is one I'm least confident in. I'll see how it evolves with time I suppose.