These works are designed in unusual ways in order to to tell their stories to the player. Some present a story out of order, overlap parts, or otherwise diverge from the standard linear method. Others limit interactivity in order to force a specific outcome and pacing.
Flashbacks. A handful of games include playable flashbacks in which the player is whisked into some past event before returning to the main action of the game.
Dreams and virtual realities. Some segments of the story are untrue within the main frame story, or there’s ambiguity about what level of reality one inhabits. Dreams and virtual reality simulations are common reasons for this.
Non-chronological narration. Events in the plot are presented out of chronological order, or repeatedly, but without any explicit flashback or frame story features. Photopia is a particularly well-known example.
Multiple endings. The game can end any of several ways; usually losing or failing endings aren’t considered valid conclusions for the purposes of counting multiple endings.
Extensive branching. Plots branch extensively, allowing the player to experience large scenes or segments of the game in different ways on different plays. More common in paper CYOA than in video games where they cost more resources to create.
Linear plots. These allow the player minimal deviation from the path the author intended.
One-move games. The piece allows only one move before ending, so the player’s experience is pieced together (typically) from a number of explorations of the same narrative moment. Aisle is perhaps the classic example of this concept.
Long-form games. It’s not really well-defined what this means, but for classic parser games it often refers to things that will take significantly longer than the IF Comp-mandated two hours to complete (usually more on the lines of 10 or more hours).
Action-limited or forced delay games. The player is only allowed a certain number of actions a day (or for some other set period), so it’s impossible to play the whole game in a single sitting. The StoryNexus system allows for this feature.
Replay-to-solve games. These are designed to be impossible to solve on a single pass and require multiple playthroughs before the player will be able to resolve the story.
Ultimate ending. There is a final “best” ending that is unlocked only when the player has experienced all of the other endings. This is a common feature of virtual novels, but rarer in the IF community.
Randomization. Some games contain portions that are randomized to allow for greater replay value; in particular, there are a some rogue-like pieces (notably Kerkerkruip) and some mysteries in which the details of the solution are dealt out randomly at the beginning of play.
Many worlds/unstable truth. Not only the player’s own actions but essential backstory features are not fixed from one playthrough to the next, so that playing multiple times can suggest different interpretations for what is happening.