I talked with a co-worker after work the other day about bout Super Smash Bros. Brawl in comparison to other fighting games. I like to talk to him about it because he is more skilled at the game than I am, and I can gain some insights into what makes the game tick. While I am certainly no expert at Smash, I admire the straightforwardness of it. Smash Bros. takes a different kind of strategy than traditional fighting games. We digressed into talking about what makes a great game, and I think that we were both able to agree that the games that were the simplest in premise but that had lots of options as to what could happen were the most satisfying games for us. I rattled off Katamari Damacy and Tetris right away, because they are games that you can explain easily. We quickly realized that we could have easily been talking about baseball or soccer or basketball.
My co-worker suggested that American Football had no hope of ever really catching on in other countries to the degree that it has in America because its rules are too complex to easily explain and games tend to run long. Then it occurred to me that those restrictions had never stopped cricket from being spread across the globe everywhere.
Then, I got to thinking about fighting games again. Why was Street Fighter II the game that took off and not Street Fighter? Why didn't they just come out with Darkhorse vs Data East 4 starring the dudes from Karate Champ, Fighter's History, Diet Go!Go! and Tumblepop squaring off against The Mask, Hellboy, Abe Sapien, and The Goon? Aside from the fact that Data East has been defunct for several years?
It's not special moves, Street Fighter had them. (Heck - Atari's incredibly lame Pit-Fighter had 'special' moves.) There is no difference between Ryu's fireball motion in Street Fighter and Street Fighter II. You rotate the joystick from the crouch position to the direction that your character is facing, and then press one of the punch buttons. The difference is that Street Fighter II had gameplay that evolved beyond the rules that the programmers gave it. It didn't hurt that it added variety in the playable characters, and made playing against human opponents more of a focus, but the animation programming of the game led to certain things behaving in unexpected ways. In Street Fighter, if you do the motion for a fireball with correct timing, a fireball surges forth from your character's outstretched hands. If your timing is incorrect, then you only see the animation for the punch button that you pressed. In Street Fighter II, if you press the jab button (the quickest, least damaging punch) quickly while doing the fireball motion, you may see a couple of jabs come out, and then the animation of the fireball motion cancels out the animation of one of the jabs. In addition, the logic for determining if you have done the motion for a special move correctly also accepts letting go of the required button instead of just pressing it, giving you a second chance to finish the motion correctly. Many special moves in Street Fighter II can cancel the animation of some of the regular moves. Also, when an attack lands on an opponent, there is a window of time where the opponent is stunned, allowing for another move to be landed in quick succession. This is referred to as a 'combo' although it has very little to do with cheese filled pretzels or how you get your school locker open. When Street Fighter II was programmed, these combos were another unknown. Hit stun and block stun were designed for making the game feel like the programmers wanted the game to feel. The combos that emerged from it were only discovered by people actually playing the game against each other. Other annoying little things were discovered like tick throws - getting your opponent to block a normal attack and then throwing them during the time that they are stunned from blocking the attack - and other variations on exploiting stun and move canceling.
Certainly, this is not the only way you come up with emergent gameplay. Sometimes, it's just as simple as leaving a bunch of objects in an environment with known individual properties and waiting to see how those things react with each other. The Grand Theft Auto games from GTA3 on are a good example of this, because the wide variety of items and environments combined with pedestrian AI behavior, although we have seen things like this before on a smaller scale. In Adventure for the Atari 2600, the erratic behavior of the bat flying around and swapping objects can turn success into death or failure in seconds.
I would contend that unanticipated behavior can come from any sufficiently complicated system. If you have only one thing in an environment, then you have only one interaction. If you have two things in an environment, you have each thing interacting with the environment plus one more interaction of the two things interacting. Three things, six interactions. Four things, ten interactions. The number of interactions increases as the square of the number of objects.
Warning: Math Content - For x objects, the number of interactions is x squared plus x all over 2. With five objects, we take 5, multiply it by itself, (that's x squared) and get 25. Add 5 more to get 30. Divide the whole thing by two, and that's 15 interactions. For ten objects, ten squared is 100, add 10 to get 110, and divide by two to get 55. There is no danger of getting half an interaction, even though we're dividing by two at the end since we're dealing with integers (whole numbers). If x is odd, x squared is also odd, so adding them together is an even number. If x is even, x squared is even, so adding them together is still even.
For those of you that skipped the math paragraph above, suffice it to say that with more stuff comes a lot more complication. Also, remember that this math having to do with interactions technically also applies to the code used to write the game in question. If the designers of a game are looking for a finely crafted experience, they usually make an effort to play test (or get their stable of testers to play test) through most of the possible interactions both as a way to make sure the game has as few bugs as possible, and to make sure some unforeseen interaction doesn't totally break the game. The play testers also have to deal with design and difficulty elements of the game, so it's not like looking for glitches are their only emphasis. With the limits of time available to make a profitable game, this means that there is limited time to do play testing, so sometimes games will ship with bugs or glitches. Sometimes the glitches are minor, and sometimes you're up to version 1.7 and every patch description starts with "Fixes exploit where..." Now, as far as I know, the Street Fighter games haven't needed major patching - even if the game has been slightly unbalanced, we as players have managed to deal with it. In light of that, maybe Capcom needs to make a first person shooter with Hadoukens.