Layered level design is all about getting more mileage out of a game's level content. The distance metaphor is an apt one. Considering the wealth of games that feature an avatar (1st person or otherwise) that moves through the game world, getting more use out of a space often times means inventing reasons for the player to travel through it multiple times.
Competitive multiplayer games get a lot of mileage out of their levels. This only makes sense. The most interesting part of such multiplayer matches is usually the opponent(s) who provides a human dynamic. Each player plays differently even from round to round thus creating play experiences that are never repeated.
Single player games (and co-op games) generally provide very guided and at times scripted experiences when compared to competitive multiplayer games. Because of this trend, a given space in a single player game can have a very limited amount of uses or unique encounters. Fortunately, this is a problem that developers have been tackling for many years.
Super Mario Brothers is a platfomer balanced around the counterpoint between Mario, enemies, and the level structures. Because of the dynamic of space, moving through the game world changes the relative timing for any upcoming action. If you need more time to stomp a Koopa, just back up. But when you back up, the Koopa will continue moving. You can't backup forever, so eventually you'll have to JUMP on the Koopa. If you kick the shell, it'll travel further on the screen the longer you waited to jump on the Koopa in the first place. If you run with the shell, it may have even more screen time. The resulting effect of one action versus another can create significant gameplay differences.
Furthermore, in Super Mario Brothers, the player can use transformative powerups and organically control the difficulty level of challenges. Only Big Mario can break bricks. With each destroyed brick, the level is transformed. Likewise, the Fire Flower powerup influences players to take on the same enemies in a new way. And finally, by using the RUN mechanic, players can make their progression through a level much quicker. The added speed in turn reduces the amount of time players have to react to upcoming obstacles. Furthermore, the momentum Mario carries when running makes maneuvering more difficult.
Mario creates layers of gameplay experiences through a level design that reacts to emergence, transformations, and suspension. Mario's layered design is also mostly organic meaning you don't have to activate it. It's happening all the time. Besides Mario, folded levels are inherently 2 different gameplay experiences layered over the same game space.
Co-op multiplayer, when done correctly, is a great way to extend the life of a game and to add more group fun to the experience (using the word "fun" very loosely here). However, even considering all of the co-op, co-ounter-op, dynamic, and emergent elements, adding more players in the game doesn't necessary make the challenges any harder or more interesting.
Consider how the challenges in these co-op games change with the addition of human players.
- Zelda: Four Swords: Whether you're playing with 3 other players or by yourself, there will always be 4 Links in play. In other words, when playing solo you control all 4 Links at once. Because of this design choice, the single player level design is largely the same as the muliplayer design. In fact, there are only a few challenges in the game that had to be reworked for solo play. So, though additional human players add additional human dynamics to the game experience, the game's challenges remain largely the same. Therefore, multiplayer does not add more layers to the level design. Options, yes. Laughter, most likely. Level design layers, no.
- Left 4 Dead: Going solo (without player or CPU help) won't get you very far in this game. Similar to Four Swords, when playing L4D solo, CPU controlled characters will accompany you. The game is designed around 4 cooperative players, so swapping out a CPU for a human doesn't change the challenge.
- Bionic Commando Rearmed: Enemies and bosses will take on new behavioral patterns in co-op play compared to solo play. In co-op, players must work together to take out bosses. This is especially apparent when one player dies in a co-op boss battle. All of a sudden, the boss AI/attacks will be a lot more manageable. Though I'm glad the developers made such changes so that co-op play requires some cooperation, simply changing out the AI of enemies doesn't count as layered level design. This example is more like dynamically switching game modes.
Many co-op games that are also designed to be played solo tend to only give the player advantages for playing with more people. In a shooter, you can cover each other during reloads. In an RPG, you can double team an enemy, which increases your damage dealt over time. In a platformer, you can multiply your chances of reaching a goal or checkpoint. Aside from any drawbacks due to any elements of co-unter-op design, the challenges remain the same while your team gains more options and abilities with every added player. What if a game's challenges naturally changed when more players are added into the mix? This is the basic concept behind...
(P)layered level design: when the challenge(s) of a level fundamentally and organically change with the addition of players. The additional players can be cooperative, counter operative, or neutral. This means writing some code that recognizes how many players are in a game and rearranges the puzzles, enemies, or any other gameplay element is not (p)layered level design. The level must remain unchanged to qualify.
Believe me, (p)layered level design is hard to come by. For the reasons described above, even four Swords, the king of co-op game design, doesn't provide good examples of it. So, I had to make up a few examples. Now, I'm perfectly aware that Super Mario World isn't a 4 player co-op game. Just image that it is to grasp the concepts.
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- The gray platforms fall after any player touches them. This gives the level an element of decay.
- The dewinged Koopa can land on any underlying platform and walk around without falling off of an edge.
- The screen scrolling prevents players from staying near the key hole while other players move toward the key.
- There are two challenges to this level section. 1) Getting all players across safely. 2) Getting all players back with a key.
- For one player, things are pretty simple. All the paths are equally viable. Pick one and platform across. Because there are two main paths (#1 and #2) the player can pick up the key and take the untraveled path back.
- With two players, both players have to be more careful. With a bit of skill, both players can use the Koopa to get across (path #2) and then platform together on the gray platforms to get back with the key.
- With 3 to 4 players, making it across is very difficult, but making it back with the key is nearly impossible. That is, unless players use co-op mechanics like picking each other up to platform 2 at a time. Using this co-op mechanic makes this 4 player challenge more like a 2 player challenge. Players still have to be careful. Without tight cooperation, one player can easily sabotage the others.
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- In this familiar set up, Banzai Bills race along the ground. Players can't RUN/JUMP high enough to JUMP on top of the Bill. By taking cover in the ditches, players can pass underneath the Bills safely.
- The ditch at #1 is only big enough for 2 players. The ditch under #3 is only big enough for 1 player. The ditch under #3 can be seen from the ditch at #1.
- Once again there are two gaols. 1) Making it across the level safely with all players. 2) Making it back safely with all players with the key.
- A single player can play through this level section pretty easily. By moving forward in the gaps between Bill shots, the player can safely make it across the level and back.
- With 2 players things are a little trickier. The player in the front must get inside the ditch and move the spring to make room for the other player. Because the second ditch is only big enough for one player, in the interims between Bills, the players must coordinate using the spring pad to send one or more of them up to the top level (path #2). The enemies on the top level are easy to dodge, but difficult to kill. Once the Koopa get inside their shells, they'll move toward the player and most likely fall down to the bottom level. This can be deadly for any player ducking in a ditch waiting for a Bill to pass by.
- For 3-4 players, most of players have to maneuver to the top level to stay safe. If at least one player doesn't stay down with the spring, someone will eventually have to travel back on the bottom level after getting the key to reach the spring. Coming back, the shells will make ducking in the ditches very dangerous (path #3). To make the trip back easier, a Starman will do the trick. To reach the Starman, the player on bottom must carry the spring with them to the key and then pass it up to the players waiting on the top level. They can use the spring to reach the item block. Getting back to they key hole from there should be easy.
And that's (p)layered level design. The more players you add, the more interesting things become. The trick is to designed challenges that decay or influence players to take advantage of the power of the group. New Super Mario Bros. Wii is said to be designed for 1, 2, 3, and 4 players. Could that mean it has (p)layered level design? We'll know soon enough.