Alchemisties

Alchemisties is a single-player collectible card game where every card is real chemistry.

Hydrogen is a 1-cost 2/1 because hydrogen is cheap and everywhere. Uranium costs 8 because it is rare and it is heavy. Put two hydrogens and an oxygen on the table and they make water — not because a designer decided so, but because that is what they make.

Nothing in the set is invented. Every molecule passes a bond-closure solver before it can be printed on a card: if the valences do not close, the card does not exist. Costs are derived from crustal abundance and atomic mass rather than hand-tuned, so the price of a card is a fact about the element, not an opinion about the game.