Collectible card games are challenging, widely played games that have received increasing attention from the AI research community in recent years. Despite important breakthroughs, the field still poses many unresolved challenges. This work aims to help further research on the genre by proposing a taxonomy of collectible card games by analyzing their rules, mechanics, and game modes from the perspective of game-playing AI research. To achieve this, we studied a set of popular games and provided a thorough discussion about their characteristics.

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There's a lot that is surprising about Marvel Snap, the new free-to-play digital card game from one of the minds behind Hearthstone (and the money behind TikTok). A match takes just five minutes. Both players play their cards at the same time. Perhaps the biggest surprise, as the game launches its second monthly season, is that it's really, really good. I spoke to Ben Brode, the co-founder of Snap's developer Second Dinner, about what Snap is, how the team set out to fix the problems of existing trading card games, and where they're going from here. The rules of Marvel Snap are endearingly simple, especially compared with the complexity typical of card games.

Eight years ago, Blizzard Entertainment launched Hearthstone, a free-to-play smartphone game that took elements of physical card battlers such as Magic: the Gathering and the Pokémon trading card game, and married them to the developer's Warcraft franchise. The result was a spectacular global success that inspired an endless slew of similar deck-building games, all based around the same idea: you start with a small pack of digital cards, each with different powers, and you place them on the board against an opponent with a different deck. Designed by Ben Brode, one of the co-creators of Hearthstone, Marvel Snap is a fresh take on the genre, in which players build collections of superheroes, each with different power ratings, and battle with a human or AI opponent to control three locations in the middle of the game board. The beauty is in the stripped-down simplicity of the interface: there are only six turns in each game, and only four cards can be placed at each location. As rounds progress, participants are able to place more powerful heroes.

In most popular card games, playing against friends is the core appeal. "Marvel Snap," on the other hand, is entirely digital and uses a simple online ranked ladder system that matches you against random opponents of a similar skill level. It's easy to slip into the game's compulsively svelte six-turn rhythm, but it's also only natural -- while watching a friend on their phone, in their match, open with a tried and true Squirrel Girl gambit, producing multiple squirrel tokens to rack up points alongside their queen -- to say, "I could do that better."

In "Marvel Snap's" sole game mode (for now), players rank up based on the number of cubes to their name. Cubes are won and lost in matches and the numbers vary on how long each bout goes and the utilization of the "Snap" mechanic. Games typically last a maximum of six turns. At any point, a player can Snap to put more cubes at stake. If one person Snaps, it suggests to the opponent that they're confident they're going to win, thus making the risk of cubes a calculated gamble.