Action Cards is an abstract, low-detail, high-trust RPG system. While characters still use an essentially random system to determine results of conflicts, they can influence those results through narrative, tailor their possible results to their character, and develop a customized character sheet.
Players build their characters out of two things: a character sheet- which has a handful of basic details- and a deck of homemade cards. A player distributes successes and failures across those cards, adds cards unique to the character, and through experience tunes abilities. The GM has his own universal deck used for opposed tests and resolution.
While each version has had some tinkering and new systems added to fit with the genre, the core mechanics remain the same throughout. The game aims to give players ownership over the narrative and a parallel feeling of ownership over their results through the use of the cards. Some versions of the system add additional chrome such as profession tracks, card-based experience, diced damage and so on.