This is stuff related to playing cards. Either writting rules that I have played for posterity, or rules I made up and wanted to write somewhere even if I never tried them out.
Those are games meant to be played with a french-suited (aka "standard") playing cards.
President, a game that I played a lot in college, putting our local/house rules here for posterity. Comes with a variant I made and actually played with people.
3 Piles, original game that I actually played against a human. Most fleshed-out rules of my original games.
7 & 8 Poker, original Poker (Pagat link) variant with combinations of only 2 cards. Mostly as a bot exercice that didn't pan out. Inspired by a 2-cards poker variant that I can't seem to find again.
Mulligan (@KaitlynEthylia), it's about sculpting a poker hand by auctioning cards in your hand to other players.
David Parlett's original card games, there's a ton of them here. Some that I liked are Sneak (I played this one!), Counterbluff (played this one too!), Abstrac, and Dracula.
The badly-named "fantasy deck" is a custom playing card game I had in mind for world building purposes (which I haven't actually used yet). It's inspired by Mahjong tiles somewhat.
It's a 60 cards deck, with 4 suits of 15 cards each. The ranks are Blank (acting as 0 or jokers), numbers from 1 to 12, Flower, and Dragon. The suits are Star (blue), Leaf (green), Sword (red), and Coin (yellow).
The flowers and dragons are specific to each suit, supposedly referencing actual and/or mythical flowers and dragons in the fantasy world.
Star dragon is benevolent, representing curiosity, wisdom, and similar stuff.
Leaf dragon is benevolent too, representing nature, growth, that kind of stuff.
Sword dragon is malevolent, representing war, violence, conflict, and other similar things.
Coin dragon is also malevolent, representing greed, selfishness, manipulation, that kind of things.
Multiple cultures in that fantasy world would skew and twist some of these interpretations in accordance to their values, but I haven't really given much thought to that part.
Here are some games I made up to play with it. Note those aren't fully fleshed out and also I've never actually played any of them with humans.
Fishing dragon, game inspired by Koi-Koi (Pagat link). The scoring part needs more work but the base is here.
Fig, simple game inspired by the Pig dice game and Blackjack (Pagat link).
Dragonshine, game loosely inspired by Gin Rummy (Pagat link). I am not sure the notes I had for it are complete, but I'm still presenting it.
An esoteric deck I had in mind also for world building purposes, inspired by Hanafuda cards and browsing the wikipedia page on astrological signs (mostly because I thought the symbols looked cool).
Read about it on its own page here, explaining its content isn't very compact.
Here are some games I made up to play with it. These also aren't fully fleshed out and also weren't played with actual humans.
Bellona, game kinda inspired by Durak (Pagat link) and Koi-Koi (Pagat link). The scoring would need some tuning, and it could also use actual playtesting.
Annarius, a 2-players trick taking game where you try to win differently in each of the 4 seasons. The scoring would need some tuning, and it could also use actual playtesting.
Propheta, a trick taking game where you try to predict specific events related to the tricks to score. The scoring would need some tuning, and it could also use actual playtesting.