In the latest episode of DLC Podcast (#137) a commentator asked, since nobody really seemed to have terribly high expectations of new Sonic games, what they would do to re-invigorate the series. Well, what is an armchair game designer to do with a question like that except bite into it?
Sonic: Unity has three main themes; freedom, personality and consequences. There are several player characters and some number of "enemy" characters on a meta-map (where you select zones: green hill zone, etc). Before you challenge your current zone, you have to select a destination, and that is where you are running "to" during your stage (but this, unlike many things, does not change the stage). Along the way, as per classic sonic you may collect enough rings to challenge for Chaos Emeralds, one per zone; however, unlike in classic Sonic, the other characters may also search out emeralds. In the beginning of the game, only Eggman will do so, but as things progress, others will as well.
Once more than half of the Chaos Emeralds have been collected, the Master Emerald starts to awaken and hunter characters like Knuckles and Shadow begin to hunt down the Emeralds. During this phase of the gameplay, all zones begin to change. Whether a zone changes and what form it takes depends on the chaos emerald whose color matches the color of the zone. If the emerald is still sealed, the stage is normal; if the emerald is held by a character, it is extremely favorable to that character and unfavorable to others. When the character runs through his own Zones, he can also spend rings to attempt to reach the Master Emerald; when there, he can either drain power from it into his own emerald (some enemies do this) or place the Emerald there for safekeeping. If the emerald has been returned to the Master Emerald, its zones are "Ascended": healthy, and any players allied with the keeper of the Master Emerald (usually Knuckles) can avoid spikes or other traps during their run. If it has been put by Eggman or Tails into one of his machines instead, the zone is "drained": broken up, drained of color, and full of robo-enemies. If the Emerald has been empowered from the Master Emerald, it becomes a warped version, and the character can uncover secrets that allow him to change zones rapidly, attack other characters However, the character who Empowers an emerald will gain a permanent bonus.
A large part of the point of this mechanic is replayability; even assuming Sonic starts in, say, Green Hill Zone, he can go to any adjacent zone, and one Zone will randomly become drained by Eggman on the first turn no matter what he does. Depending on which emeralds Sonic gets, and which emeralds Eggman gets, and in what order, the player may see different versions of each Zone on each playthrough, and cannot see every version of every zone in one playthrough. Assuming he doesn't try to see as many zones as possible (by ignoring the plot), he can have vastly different runs each playthrough.
Sonic can only interact with other characters when they enter the same Zone, or two crossing Zones. He may attack, befriend, or attempt to manipulate characters based on their wonts and needs; for example, he can tell Knuckles to chase someone with an Emerald (if Sonic does not have one, or by proving that he and Knuckles are on the same side by returning Emeralds to the Master Emerald). Friends can tag along and the player can switch to friend characters, up to three characters in a team; friends may leave after (or in the middle of) a zone to pursue their own interests. Attacking characters forces the loser to drop Chaos Emeralds, and can banish a weaker enemy. Emeralds put into machines create boss characters that must be defeated (exception: Tails can remove the Emerald from his machines)
Each course, and each version of each course, is designed around a few platforming mechanics; each character is missing some of these mechanics. The mechanics are Dash-ball, Wall-climb, Fly/Doublejump, and Ground-pound. Friends cannot automatically pass some zones that the player can pass; the player can spend rings at a checkpoint to warp them forward, otherwise the friends part ways when the player passes the end gate.
Here are example characters and, for AI controlled characters, how they normally behave (over the course of many turns):
* Sonic (DB,GP): Once he encounters any zone that has been warped or drained, he will attempt to return all Emeralds to the Master Emerald. His main goal, however, is to defeat Eggman.
* Tails (DB,FD): Only rarely goes looking for Emeralds. If he gets one, he will put it into a machine. If he is told or discovers that this has warped a Zone, he will give away all Emeralds to anyone who asks, and will dismantle any machines he has made..
* Eggman/Robotnik (WC,GP): Gets an emerald first turn and puts it into a machine. Periodically repeats. Never allies with Sonic or Tails. His main goal is to have all Emeralds in Machines.
* Knuckles (WC,FD): Appears after the Master Emerald awakens. Chases any character with a Master Emerald; 50% chance to attack vs ask for the emerald. His main goal is to return all Emeralds to the Master Emerald. If you get an Emerald while he is your friend, he will take it and may immediately leave.
* Shadow (WC,GP): Appears after the Master Emerald awakens. Searches for Emeralds, attacks characters to get Emeralds, and will attempt to empower emeralds. Will never willingly return an emerald.
* Rouge (WC,FD): Appears randomly. Will always ask for Emeralds, and has high success rate against most male characters. Can be convinced to give up emeralds if she is in a warped or drained zone.
* Amy (WC,GP): Occasionally appears and befriends Sonic without his consent. When she meets any other Good character, she may befriend them at random. Will look for Emeralds if Sonic asks, may look if other players ask. Will give up Emeralds to anyone who asks. Automatically gives Emeralds to Sonic.
An example of the different versions of a zone:
* Green Hills, Favorable (emerald held by player): Terrain is generally more level, with fewer obstacles, and enemies generally spawn out of the player's normal path.
* Green Hills, Unfavorable (emerald held by other): Several sections of ground are moved up or down relative to their normal position making it difficult to traverse normally. This also opens paths to hidden ground zones.
* Green Hills, Drained (emerald in robot): All grass and trees are gray and withered. Loops are crumbled and have become either background features or hazards. Extra spike traps. Many higher plateaus are simply gone; terrain is generally more level.
* Green Hills, Warped (emerald empwered): In many places grass is on fire. Many sky platforms exist, and some areas have altered gravity. Some difficult paths to hidden ground or sky zones. Traversing normally is dangerous.
* Green Hills, Ascended (emerald returned): Background is especially lush. Fewer dead ends, some extra paths and some sky platforms, including passages to hidden sky zones.
The game is generally set up so that the player cannot succeed without multiple good characters undertaking missions at the same time, in particular because multiple bad actors may be acting at any time. This is accomplished by making allies with other characters; doing what they want, asking them to do what you want, and generally coordinating your actions with the AI (or, optionally, other players). In principle, this means that some of the "story" going on in the game happens between two non-player characters, which may be revealed between zones with a little skit (for example, Tails or Amy giving an emerald to Eggman simply because he asks, then immediately regretting it; alternately, a character beating an enemy robot and taking its emerald).
I said earlier that the themes were freedom, personality, and consequences. Each character is free; they choose a side based on what they want or don't want, and may change sides when they discover the consequences of their actions. (Some characters, like perhaps Shadow, will switch away from the side of "good" if something happens they don't like; Knuckles will very frequently betray anyone who keeps emeralds even if he previously considered them a friend). The characters do not start omniscient and have to discover each other's natures as the game progresses.
Each character has one win condition, and only one character may win:
* Sonic must defeat Eggman in his sky fortress (by unlocking several sky zones using Favorable or Ascended levels)
* Tails must discover a way to destroy the Chaos Emeralds (by possessing each at least once, draining and warping emeralds at least once) so that he can break the cycle.
* Robotnik must create a robot using the Master Emerald (possible once every emerald has been in a robot at least once)
* Knuckles must return all emeralds and protect the Master Emerald at all costs.
and so on.
The idea has a lot of holes in it, but as a starting point, I like the idea that the emeralds--and who owns them--change the world. I also like the idea that the various characters in the world can be off doing something interesting while Sonic continues his main quest, and that there are reasons for characters to not hold on to chaos emeralds forever. And the game, fundamentally, can be done in old-school 2D sonic fashion, with old-school mechanics, without making the game as repetitive as classic Sonic.
Perhaps most of all, good characters can be good, bad characters can be bad, friendship can win the day, and it can be, you know, maybe, not written terribly, because there is no need to force everyone to be in one place all the time. People can go their own way, do their own thing, and it all comes together eventually.
I dunno. I might clean the concept up later and try again.