The winner of the 2012 Independent Games Festival Nuovo Award, the IGF's award for best esoteric or "arty" game, was a funny little game called Storyteller. Presented with a few panels and some characters and props, you have to arrange those characters in the panels to tell a story like "jealousy leads to a double murder."
To tell the story you have to place the items in a logical sequence. A tombstone placed in the third panel simply sits there and does nothing on its own. But when placed after a panel with an unsuspecting hero and a murderous villain the tombstone automatically shows the face of the innocent (now murdered) hero.
Since all the characters in Storyteller behave in pre-scripted ways, unusual combinations can result in stories you hadn't intended to tell. When I stopped by the Storyteller booth at IGF I watched a player place a villain inside a cage with the hero standing next to him in one panel. In the next panel the player placed his hero character again along with a box of treasure. The player was, I believe, attempting to give his hero a happily ever after scenario where he gained riches for his good deeds. But with the villain gone in the last panel Storyteller told the story differently, adding the caption "Tim sold Adam."
Storyteller's unexpected twists are an example of emergent gameplay, where a simple set of rules results in gameplay by users that the creator hadn't intended. The emergent aspect of Storyteller is relatively minor but as I wandered the show floor at GDC I found more and more games with emergent mechanics.
Emergent design is popular with indie developers for a lot of reasons. The simple rules of emergent games fit the "creativity over all" ethos of indie gaming where a good idea is more valuable than programming skills. It also encourages players to play creatively and explore the limits of the game system. Perhaps most importantly, emergent games are a way to fight back against the rising cost of game development for a community that often doesn't have the cash to spare.
Consider that Mass Effect 3, Bioware's epic ending to the company's sci-fi RPG trilogy, features over 100 hours of recorded audio from voice actors covering all the different possible combinations of NPC reactions to your character and its choices. Your protagonist can only have two companions with them and can only make one choice at a time but Bioware has to record options for every choice for every companion and those reactions cost money to write, record, and program into the game.
This is why Mass Effect 3 and other AAA titles like it cost tens of millions of dollars to develop. In contrast, an emergent gameplay system is much simpler to program. Once the simple rules are established developers can concentrate on showing what their game can do and don't have to worry about programming for every eventuality. Essentially, designers can save money by letting the players create their own fun instead of pre-programming in every choice a user could possibly make.
The king of emergent gameplay at GDC was Johann Sebastian Joust, a game played with a laptop, a few PlayStation Move controllers and no screen of any kind. Joust is played to the tempo of a piece of music (often a snippet of a Bach classic). As the music speeds up you can move your controller faster without being knocked out of the game, but when it slows down the Move controller's tolerance for motion drops down as well. The goal of Joust is to knock other players out of the game without being knocked out yourself, and what makes the game unique is that there are absolutely no rules for how to do this.
In a way emergent gameplay is the only kind of gameplay that Joust has. Without any rules to guide the player they have to invent their own. Players can hit each other, toss objects in another player's direction, hide their controller or themselves to try and wait out the other players.
The result is a an amazingly addictive game. I've gotten two chances to play it this past week and both times I had trouble pulling myself away when it was time to go. It's the open-endedness of Joust that makes the game so entertaining. There are so many possible strategies that you constantly want to play another round just to see what would happen if you tried to declare a temporary truce with your neighbor or decided to kick the controller out of your opponent's hand.
Of course there's no reason a game a story-driven big budget title can't have emergent gameplay as well. I'd cite Portal and Portal 2 as titles that have a great story and some great emergent solutions to their puzzles. Still it's a design philosophy fewer and fewer big-budget titles seem interested in and I think it's effecting more than just the bottom line.
I've been playing Mass Effect 3 since GDC ended. Without a doubt it's a fantastic achievement in game design, wrapping up the stories and characters I've grown so invested in over the last two games. But I keep bumping up against the edges of the game, finding story decisions I can't make or that I wish had gone a slightly different way. Bioware's come as close as any game company in history but it's impossible to tell a story that everyone likes. Maybe the solution is to let the players make their own.