I was giving the Physics Guide a read so that I can understand Sonic's motion play better. And I really need to congratulate @Lapper and @Mercury on the amazing job both of them did on it! It's God's work, and the overlay scripts are really revealing, like seeing the threads behind a marionette. It's fantastic, really, especially the fact that even someone like me can get it somehow. I'm terrible with numbers, so to make me understand something that uses them that extensively is quite a feat! So what I'm trying to make is a description of the general principles of Sonic's entire gameplay system for Classic Sonic (and I know a lot of exceptions to these will exist, especially in Sonic 3&K). Now why do this anyway? I think it's useful for a few things. First, it allows us to open dialogue with any other gameplay styles, including Sonic's modern and alternative ones, because they can be described using similar terms, and that allows any exchange -- critical or creative -- to be more fruitful. It's a general approach to comparisons we often make using "local" terms; Second, it allows us to analyze Sonic's classic gameplay without preconceived value judgements. Having all this doesn't make a "good Sonic game", but it helps us identify core aspects of this said gameplay style, which ones still persist, which ones were abandoned etc.; Third, it allows us to formulate some chains of causation. This is not the only way one could have worded any of this. You could start with what you see on the screen and go from there. You could start with the core mechanics and reach the objectives afterward. This is almost ideological, but the way I formulated subtly implies the core mechanics are at the core because they're what makes objectives possible. If you start from the core mechanics until you reach the objectives, you subtly imply they are more important. This distinction is absolutely huge, and a very important part of general formulations. This can help creatives select what they'd like to focus on when making new fangames and not stray from there, messing with the original rules more consciously. For a very basic example, people all say lives are an obsolete mechanic, even for classic Sonic, and will either do away or call for doing away with them. This formulation helps to see clearly what removing them means, how this affects progression and other gameplay mechanics. So it leads us to better informed opinions on how or why Classic Sonic as a whole, and not just one aspect or other, works. For another example, each and every rule here can be simply ignored or redacted. Sonic doesn't need to be teleported to his last checkpoint when dying (like shmups usually don't do), and objects don't need to not interact with each other in a stage. A badnik could be able to kill another badnik or collect ringss by themselves, why not? Knowing which rule you're subverting leads to a consistent approach to innovation to the gameplay. Of course, game design and developemnt is generally iterative and experimental, but this can help too! So here's what I have so far: Classic Sonic General Gameplay Spoiler: Objectives A player starts a game with a score count of zero, a credit count of zero and a default life count above zero, usually three; A player can only control Sonic's movement and the way he'll interact with the action space and its elements; The player may sometimes be able to control other characters, such as Tails or Kmuckles, but since their gameplay rules derive from Sonic, we'll refer only to Sonic for simplicity's sake; A player beats the game by clearing all stages sequentially, in a predetermined order; Stages are usually called "Acts" and grouped within Zones with similar themes, action space geometries, enemies and gimmicks. Generally, at least in the last stage of a group, there will be a boss fight; A stage is considered cleared when Sonic touches a signpost object, generally unique and located at the rightmost point of a stage's action space, or when he hits a capsule, generally after a boss fight is cleared; A boss fight is an encounter with an enemy that has a binary outcome: either it is cleared or Sonic dies, and it can generally only be cleared by destroying them. The method by which a boss fight is considered cleared varies, but most times it happens by hitting its vulnerable spots enough times, usually eight; After a stage is cleared, both the ring and the time counter are reset to zero, the game proceeds to the next stage and saves the progress; Progress is also saved when Sonic touches a checkpoint, which then can't be touched again even if the stage resets, as well as all the other previous checkpoints in a stage's predetermined order; As a player clears all the stages, the game will check if Sonic has all the available Chaos Emeralds (this name will be used for Time Stones too); if so, the game considers it reached a Good Ending; otherwise, it considers it reached a Normal or a Bad Ending; either way, the game will then reset; A player can get a Chaos Emerald either by clearing a Special Stage, or by collecting it in a regular stage like a normal object; The methods for clearing Special Stages can vary wildly across games; Failure conditions for Special Stages vary wildly too; Either way, the ring count resets to however much Sonic had before accessing the Special Stage, and Sonic returns to where he was right before accessing the Special Stages; The methods for accessing Special Stages can vary a lot between games, but are usually centered in: Having a ring count equal or above a certain threshold, usually 50, when clearing a stage or touching a checkpoint; Touching a special object in a stage; A player loses the game if the life count and credit count both reach zero; the game will then reset; If the life count reaches zero, but the credit count is above zero, the player can choose to continue the game: If they do, the current stage resets, the player's score count resets to zero and their life count resets to the default number, usually three; then the payer's credit count is depleted by one; If they don't, the game will then reset; A player can increase their credit count in a Special Stage by completing a task, usually a performance metric, that is normally unrelated to getting Chaos Emeralds; A player can only decrease their life count by dying, which can happen in multiple ways: By taking damage while Sonic's ring count is zero; By letting the time count reach an upper limit, usually 10 minutes; By touching the bottom limit of the action space; By being pushed by the stage's geometry or by an object into a space smaller than Sonic's hitbox; By running out of air; Besides depleting Sonic's life count by one, dying returns the stage to its initial stage and sends Sonic to where his progress was saved the last time, then resets Sonic's ring count to zero; A player can increase their life count in multiple ways: By having the ring count reach a multiple of a certain number, usually 100, on a stage (once per multiple per stage); By destroying an 1-Up monitor; By having the score count reach a multiple of a certain number, generally 50000; A player can increase their score count in multiple ways: Once a stage is cleared, the time counter stops and the score count is increased according to the player's metrics: The score count increases by a multiplier, usually 100, of Sonic's current ring count; The score count increases according to a predetermined value based on the time count, which varies across all games -- the lower the time count, the higher the score. The score count may be increased at a fixed rate according to the presence of certain bonuses and effects on Sonic as he clears the stage, such as a shield; Once a Special Stage is cleared, the score count is increased according to the player's metrics: The score count increases by a multiplier, usually 100, of Sonic's current ring count; A player can also increase their score count by destroying objects. Usually, the score count is increased according to a combo system based on how many objects Sonic has destroyed before either uncurling or touching the ground. The minimum amount by which the score will increase this way is usually 100, and the maximum is 10000; A player can also increase their score count by collecting or hitting certain objects. The minimum amount by which the score will increase this way is usually 10, and the maximum is 10000; A player can increase their ring count by collecting rings, which are floating, unmovable objects sitting on an action space, or by destroying a Ring Monitor; Spoiler: Core Mechanics Each stage has an action space -- a stage map -- which limits Sonic's movement in all directions. Within these limits, there is terrain on which Sonic can stand and move. Chunks of terrain can float on the air and move on their on; The action space has a layer system that allows Sonic to move through terrain under certain circumstances, so not all terrain is solid at all times; Sonic is framed at a portion of the action space surrounding him, and that frame will automatically keep up with Sonic's movement, generally trying to keep him within margins at its center; Sometimes, most commonly in boss fights, that frame will also bind Sonic's movement to its limits, effectively pairing Sonic's action space with the screen space; The action space may sometimes wrap around itself on one axis, making it functionally infinite; The player can move the frame by looking up or by curling while not moving; Sonic starts a stage at a fixed point in the action space, generally near the leftmost point, and can move toward the goal by running, jumping and curling. Any other action Sonic can make, such as rolling or spindashing, is a compound of these; each of these actions change his horizontal and/or vertical speed through acceleration (as opposed to a direct change from input); All these actions are subject to acceleration, both from input and from gravity -- whose force points toward the bottom of the screen; in turn, this makes it so that sloped terrain interferes directly with movement. It also makes it so that longer presses increase or maintain acceleration for longer; Sonic has two vulnerability states, "vulnerable", and "invulnerable"; two attack states, "non-destructive" and "destructive"; two self states, "uncurled" and "curled"; and two movement states, "ground state" and "air state"; this gives us a total of 16 unique states Sonic can be in. (Well, actually 14, because it's impossible for Sonic to be simultaneously curled and non-destructive while in the air); Sonic will generally start a stage vulnerable, non-destructive, uncurled and in ground state; There's a state that modifies both movement states, which happens when Sonic goes underwater. For simplicity's sake, they won't be considered separate movement states. When underwater, Sonic's acceleration is decreased all across the board, and if Sonic spends enough time underwater withut either ging out of water or collecting a large air bubble, usually thirty seconds, Sonic dies; When uncurled, Sonic has a standard hitbox size and running will accelerate him in the direction of the payer's input, even if he isn't moving; when curled, Sonic's hitbox is smaller and the effect of the ground's angle on his acceleration is accentuated. Sonic can go from "ground state" to "air state" either by jumping, or by running or rolling out of a non-smooth surface, and the resuting velocity vector incorporates the horizontal and vertical speeds he had at that moment; In Sonic's air state, input can still control his horizontal acceleration. However, he's subject to air resistance; Jumping affects attack, self and movement states, making him curl and launching him to the air; Jumping causes Sonic to move away from the ground at a normal angle towards the ground regardless of the terrain's angle itself; Rolling is what happens when Sonic curls while running, so unlike jumping, it's an effect rather than a single action. It affects Sonic's attack state, setting it to "destructive", and affects Sonic's acceleration according to the angle of the surface he's on, further accelerating him in the direction of gravity's force. If he's on a flat surface, it slows Sonic to a stop, even if there's still pressing a horizontal input, and he'll uncurl. Sonic's only possible method of interaction with the stage is through collision with his own body, except in rare circumstances, and that interaction can have multiple effects. In general cases, interacting with an object will cause him to collect, hit, bounce from, take damage from or push them, and that depends on the properties of each object: Collecting them eliminates them from the map, but doesn't affect Sonic's movement at all (except for big air bubbles, which set Sonic's velocity to 0). It's done in any of Sonic's states upon collision; collecting a ring increases the ring count by 1, and collecting a Chaos Emerald will increase its count by 1 too; collecting an air bubble resets the time Sonic can spend underwater withut dying; Hitting an object happens when Sonic touches an object that also has vulnerability and attack states. Then, Sonic's vulnerability and attack state values are compared to the object's: If Sonic's attack state value is "destructive" and the object is "vulnerable", the game depletes one hit point from the object and makes Sonic bounce off it regardless of the object's attack state. This also happens is Sonic is "non-destructive", but the object is also "non-destructive" and "vulnerable" If an object's life count reaches zero, it's destroyed, which eliminates them from the map while keeping whatever horizontal speed Sonic had at the time and, if Sonic is falling, reversing his vertical speed. If Sonic is "vulnerable" and the object is "destructive", Sonic takes damage; If Sonic is "invulnerable" and the object is "destructive", either nothing happens to Sonic's movement or he collides with it like any other solid object; Taking damage stops Sonic's movement, sends him flying backwards, makes him "invulnerable" for a while and removes Sonic's shield. If Sonic doesn't have a shield, damage depletes all rings from the ring count, and rings spawn from Sonic, scattering around the screen and bouncing around until disappearing after some time, during which they can be recollected; if a player had a ring count of zero, Sonic dies instead; Bouncing from an object changes Sonic's vertical and/or horizontal speed. Each object has a particular behavior. Some objects accelerate Sonic in a specific direction by a specific amount, uncurling him and making him vulnerable while doing so, like springs; others apply acceleration to the opposite direction of Sonic's movement; there isn't a clear pattern to their behavior; Pushing is special in that only certain objects can be pushed. Doing so moves the object in direction of the input upon collision, at a fixed speed. Some objects can push Sonic, too; Not all objects are homogeneous in their vulnerability states. An enemy can have a main body that is vulnerable and destructive, and have an appendix or throw a projectile that is destructive and invulnerable; These appendixes and projectiles can't be interacted with if Sonic is invulnerable; Some objects have special effects upon being hit, and some have special effects upon being destroyed. These effects vary, but here are some examples: Increasing the score count; Giving Sonic a shield; Increaing the ring count by any number, usually 10; Increasing Sonic's life count; Increasing Sonic's acceleration across the board and top speed for a limited amount of time; Setting Sonic to "invulnerable" and "attacking" states regardless of the player's actions for a limited amount of time; Making Sonic take damage; Special objects can change Sonic's possible actions, and are considered gimmicks. How they change the possible actions varies wildly from stage to stage and from game to game, but the method of interaction is always collision between these objects and Sonic; If Sonic has seven Chaos Emeralds and a ring count higher than a certain threshold, usually 50, he is capable of performing an additional action, Super Transformation. This action locks Sonic in his "invulnerable" and "attacking" states regardless of all his other states, and increases his acceleration across the board; this also decreases his ring count by one every second. If the ring count reaches zero, the effect ends; A Special Stage (bonus stages also fall in this category) is a stage with rules and core mechanics that usually deviate from the rules and core mechanics described here; Rules for Each Game Spoiler: Sonic the Hedgehog (Mega Drive/Genesis, 1991) [WIP] Objectives A player starts a game with a score count of zero, a credit count of zero and a life count of three; A player beats the game by clearing all nineteen stages sequentially: Stages are called "Acts" and grouped within six Zones, with three Acts each, and one Zone with a single Act: Green Hill Zone Marble Zone Spring Yard Zone Labyrinth Zone Star Light Zone Scrap Brain Zone Final Zone A boss fight occurs at the last Act of each Zone, except for Scrap Brain; A stage is considered cleared when Sonic touches a signpost or when he hits a capsule; Capsules appear after boss fights are cleared; signposts appear in stages without boss fights; A boss fight is an encounter with Dr. Eggman that has a binary outcome: either it is cleared or Sonic dies, and it can only be cleared by destroying them. Sonic can destroy them by hitting them eight times; The exception is the boss fight in Labyrinth Zone, which doesn't need to be destroyed for Sonic to be able to hit the capsule; As a player beats the game, they may get a Good Ending or a Bad Ending depending on how many Chaos Emeralds the player has collected: A Good Ending happens if Sonic has collected six Chaos Emeralds; A Bad Ending happens if Sonic has collected less than six Chaos Emeralds, and a screen with Eggman juggling the emeralds Sonic didn't collect, telling the player to try again; Either way, the game will then reset; Chaos Emeralds can be collected by clearing a Special Stage: A Special Stage is considered cleared if Sonic touches the Chaos Emerald in the Special Stage map; A Special Stage is considered failed if Sonic touches a "Goal" object in the Special Stage map; Either way, the ring count is reset to zero, and the player returns to where they were in their progression in the stage sequence; A player can access a Special Stage by having a ring count of 50 as they touch a signpost, then touching a Warp Ring above it; A player loses the game if the life count and credit count both reach zero. The game will then reset; If the life count reaches zero, but the credit count is not zero, the player can choose to continue the game: If they do, the current stage resets, the player's score count resets to zero and their life count resets to three; then the payer's credit count is depleted by one; If they don't, the game will then reset; A player can increase their credit count in a Special Stage by having a ring count of 50 or more rings at the end of a Special Stage; A player can only decrease their life count by dying, which can happen in multiple ways: By taking damage while Sonic's ring count is zero; By letting the time count reach the upper limit of 10 minutes; By touching the bottom limit of a stage map; By being crushed, that is, pushed by the stage's geometry or by an object into a space smaller than Sonic's hitbox; By running out of air; Besides depleting Sonic's life count by one, dying returns the stage to its initial stage and sends Sonic to where his progress was saved the last time, then resets Sonic's ring count to zero; A player can increase their life count in multiple ways too: Whenever the ring count reaches a multiple of 100 rings (once per multiple per stage); Whenever Sonic destroys an 1-Up monitor; Whenever the score count reaches a multiple of 50000; Once a stage is cleared, the time counter stops and the score count is increased according to the player's metrics: The score increases by 100 times Sonic's current ring count; The score increases according to a predetermined value based on the time count: 50000 points for a time count of 0:29 and under; 10000 points for a time count between 0:30 and 0:44; 5000 points for a time count between 0:45 and 0:59; 4000 points for a time count between 1:00 and 1:29; 3000 points for a time count between 1:30 and 1:59; 2000 points for a time count between 2:00 and 2:59; 1000 points for a time count between 3:00 and 3:59; 500 points for a time count between 4:00 and 4:59; Once a Special Stage ends, the score count is increased according to the player's metrics: The score increases by 100 times Sonic's current ring count; A player can increase their ring count by collecting rings, which are floating objects on a stage map, or by destroying a Ring Monitor; After a stage is cleared, both the ring and the time counter are reset to zero, the game proceeds to the next stage and saves the progress; Progress is also saved when Sonic touches a checkpoint, which then can't be touched again, as well as all the other previous checkpoints in a stage's predetermined order; Core Mechanics Each stage has a map that limits Sonic's movement in all directions. Within these limits, there is terrain on which Sonic can stand and move. Chunks of terrain can float on the air and move on their on; The map has a layer system that allows Sonic to move through terrain under certain circumstances: When coing from under the Sonic is framed at a portion of the map surrounding him, and that frame will automatically keep up with Sonic's movement, generally trying to keep him within margins at its center; See SPG:Camera; The player can move the frame by looking up or by curling while not moving; Sonic starts a stage at a fixed point in the stage map, generally near the leftmost point, and can move toward the goal by running, jumping and curling. Any other action Sonic can make, such as rolling, is a compound of these; each of these actions change his horizontal and/or vertical speed through acceleration (as opposed to a direct change from input); All these actions are subject to acceleration, both from input and from gravity -- whose force points toward the bottom of the screen; in turn, this makes it so that sloped terrain interferes directly with movement. It also makes it so that longer presses increase or maintain acceleration for longer; Sonic has two vulnerability states, "vulnerable", and "invulnerable"; two attack states, "non-destructive" and "destructive"; two self states, "uncurled" and "curled"; and two movement states, "ground state" and "air state"; this gives us a total of 16 unique states Sonic can be in. (Well, actually 14, because it's impossible for Sonic to be simultaneously curled and non-destructive while in the air); Sonic will generally start a stage vulnerable, non-destructive, uncurled and in ground state; There's a state that modifies both movement states, which happens when Sonic goes underwater. For simplicity's sake, they won't be considered separate movement states. When underwater, Sonic's acceleration is basically halved all across the board, and if Sonic spends 30 seconds underwater without either ging out of water or collecting a large air bubble, Sonic dies; When uncurled, Sonic has a standard hitbox size and running will accelerate him in the direction of the payer's input, even if he isn't moving; when curled, Sonic's hitbox is smaller and the effect of the ground's angle on his acceleration is accentuated. Sonic can go from "ground state" to "air state" either by jumping, or by running or rolling out of a non-smooth surface, and the resuting velocity vector incorporates the horizontal and vertical speeds he had at that moment; In Sonic's air state, input can still control his horizontal acceleration. However, he's subject to air resistance; Jumping affects attack, self and movement states, making him curl and launching him to the air; Jumping causes Sonic to move away from the ground at a normal angle towards the ground regardless of the terrain's angle itself; Rolling is what happens when Sonic curls while running, so unlike jumping, it's an effect rather than a single action. It affects Sonic's attack state, setting it to "destructive", and affects Sonic's acceleration according to the angle of the surface he's on, further accelerating him in the direction of gravity's force. If he's on a flat surface, it slows Sonic to a stop, even if there's still pressing a horizontal input, and he'll uncurl. Sonic's only possible method of interaction with the stage is through collision with his own body, except in rare circumstances, and that interaction can have multiple effects. In general cases, interacting with an object will cause him to collect, hit, bounce from, take damage from or push them, and that depends on the properties of each object: Collecting them eliminates them from the map, but doesn't affect Sonic's movement at all (except for big air bubbles, which set Sonic's velocity to 0). It's done in any of Sonic's states upon collision; collecting a ring increases the ring count by 1, and collecting a Chaos Emerald will increase its count by 1 too; collecting an air bubble resets the time Sonic can spend underwater withut dying; Hitting an object happens when Sonic touches an object that also has vulnerability and attack states. Then, Sonic's vulnerability and attack state values are compared to the object's: If Sonic's attack state value is "destructive" and the object is "vulnerable", the game depletes one hit point from the object and makes Sonic bounce off it regardless of the object's attack state. This also happens is Sonic is "non-destructive", but the object is also "non-destructive" and "vulnerable" If an object's life count reaches zero, it's destroyed, which eliminates them from the map while keeping whatever horizontal speed Sonic had at the time and, if Sonic is falling, reversing his vertical speed. If Sonic is "vulnerable" and the object is "destructive", Sonic takes damage; If Sonic is "invulnerable" and the object is "destructive", either nothing happens to Sonic's movement or he collides with it like any other solid object; Taking damage stops Sonic's movement, sends him flying backwards, makes him "invulnerable" for a while and removes Sonic's shield. If Sonic doesn't have a shield, damage depletes all rings from the ring count, and rings spawn from Sonic, scattering around the screen and bouncing around until disappearing after some time, during which they can be recollected; if a player had a ring count of zero, Sonic dies instead; Bouncing from an object changes Sonic's vertical and/or horizontal speed. Each object has a particular behavior. Some objects accelerate Sonic in a specific direction by a specific amount, uncurling him and making him vulnerable while doing so, like springs; others apply acceleration to the opposite direction of Sonic's movement; there isn't a clear pattern to their behavior; Pushing is special in that only certain objects can be pushed. Doing so moves the object in direction of the input upon collision, at a fixed speed. Some objects can push Sonic, too; Not all objects are homogeneous in their vulnerability states. An enemy can have a main body that is vulnerable and destructive, and have an appendix or throw a projectile that is destructive and invulnerable; These appendixes and projectiles can't be interacted with if Sonic is invulnerable; Some objects have special effects upon being destrooyed, and are shaped like TV monitors, thus appropriately called Monitors. The possible effects are: Giving Sonic a shield; Increasing the ring count by 10; Increasing Sonic's life count by 1; Increasing Sonic's acceleration across the board and top speed for a limited amount of time; Setting Sonic to "invulnerable" and "attacking" states regardless of the player's actions for a limited amount of time; Making Sonic take damage; Special objects can change Sonic's possible actions, and are considered gimmicks. How they change the possible actions varies wildly from stage to stage and from game to game, but the method of interaction is always collision between these objects and Sonic; If Sonic has seven Chaos Emeralds and a ring count higher than a certain threshold, usually 50, he is capable of performing an additional action, Super Transformation. This action locks Sonic in his "invulnerable" and "attacking" states regardless of all his other states, and increases his acceleration across the board; this also decreases his ring count by one every second. If the ring count reaches zero, the effect ends; A Special Stage (bonus stages also fall in this category) is a stage with rules and core mechanics that usually deviate from the rules and core mechanics described here; I'd like to point out this isn't a work that entails just, like, translating code to English. I want to reach general expressions for Sonic's gameplay, acknowledging as many variants of the same mechanics as possible under the same concepts, thus defining exceptions as real exceptions; The most important here, I guess, is that as we look at Sonic's rules, we can take a more critical look at them. We may take them for granted and not even think about them, but each one of them had a reason to be implemented. So it's good to formulate them anyway. Some distinctions, I think, are especially important because we so often pair them up automatically ("stage" and "action space", for example) and noticing they're not necessastily the same thing can help bringing new ideas for game makers, I suppose. Also understanding how some phenomenons, like bottomless pits, aren't things in themselves but particular cases that exist because of general rules. (Also I'll feel really stupid if this already exists somewhere, laid out like this.) EDIT (230624.1): Changed "object life count" to "object hit points" to avoid confusion; also deleted most numbered instances, using them as examples instead; EDIT (230624.2): Added time overs and death by touching the bottom of the stage map, as well as applying the corrections @DigitalDuck provided. Thanks! EDIT (230625.1): Added points about underwater gameplay, super gameplay and the camera; also organized the rule structure so it can be better oriented by objectives first (the why), core mechanics second (the how). As far as I can go, I think everything is there! EDIT (230625.2): Added corrections about how score chains work, and the relationships between curling and attacking; EDIT (230626.1): Rearranged some rules so the hierarchy makes more sense. Also started describing specific games' rules according to this template, starting from Sonic 1 for the Mega Drive, so that maybe? they can help the wiki in some way; EDIT (230626.2): Added a somewhat more detailed description of what a stage map is made of, including the layer systems; EDIT (230629): Added corrections by @SyntaxTsu. Thanks! EDIT (230630): Added a correction by @DigitalDuck again. Thanks! I really need to stop pulling the rules from memory only. Also, described something that is obvious, but not a given: gravity usually pulls you toward the bottom of the screen.
In Sonic 1 and Sonic 3 & Knuckles, this is done by collecting 50 rings in a special stage. In Sonic 2, this is done by having a total combined time and ring bonus of 10000 or more. Jumping doesn't strictly preserve horizontal speed, as shown whenever you jump from a slope, unless you're referring to the speed before jumping, in which case it's both horizontal and vertical speed preserved; meanwhile, running or rolling out of a non-smooth surface preserves both horizontal and vertical speed before he accelerates downwards due to gravity (and possibly moves horizontally due to inputs and/or air resistance that applies when you're moving upwards slowly). Sonic bouncing off destroyable objects has nothing to do with his curl state; if and only if he is moving downwards then his vertical speed is reversed, regardless of his curl state. Bosses have different bounce rules in different games, but they continue to ignore curl state. It's as you say, this is a property of the object and not Sonic. Springs act one way, bumpers another, seesaws yet another, etc. If you're not going into per-object detail then this is just a case of "some objects can have an effect on Sonic's position and velocity". Unless he has a shield, in which case he loses the shield instead of rings or death. The stage is reset to its initial state, not the state it was when Sonic hit the checkpoint. All objects are restored. Also, if Sonic hasn't yet hit a checkpoint in the stage, he is returned to the start of the stage. Pushing is again a property of the object and not Sonic; Sonic does not have to be uncurled to move objects, and in some cases can push objects that can also be destroyed. The pushing animation itself is entirely separate, and is merely a "I can't walk in this direction" animation.
Then I don't think it's very much worth it to describe it because there isn't a general rule. And in any case special stages can be more or less anything, so it's impossible to determine it. Best to jut leave it as "normally you get credits in special stages for one reason or another". You're right. I mixed up horizontal speed and ground speed, which is a clearer term anyway and the one the physics guide uses. You're right! This seems like a better way to talk about these objects. They're all different, and they may or may not ignore Sonic's state (bumbers do, that armadillo badnik that acts as a bumber in Stardust Speedway doesn't, afaik), so it seems hard to unify them. I wonder if having a shield is so general a feature that it's worth describing. Like, probably, but it's a variation on something that's already at the core of the game and doesn't interfere with anything else (except in the case of elemental shields, of course). What do you say? Really? Huh. Could've sworn monitors you've destroyed stay destroyed. Maybe I'm hallucinating, or maybe it's specific to some game. (EDIT: I was hallucinating) Either way, there must be a better way to describe it because if it reset to the initial stage, the checkpoints would be reset too, but they don't (at the very least, the one you return to. Now that I think about it, I never tried backtracking to a previous checkpoint after dying just to see what happens to it) (EDIT: that doesn't matter much, you can describe what happens saying just that). I see! Though I didn't know you could push objects while uncurled. What's more! I just tried it on the pushable block in Marble Zone Act 1 and, while you're pushing, rolling withut an input doesn't even decelerate Sonic. He'll just push the block indefinitely. So a funny quirk there. ----------- EDIT: Actually I've started to think you can't really describe the way Sonic vulnerability works with the way he can attack under the same concept, because invincibility frames and invincibility from a monitor work differently. Both prevent damage, but only one puts you in permanent attack mode. Bummer.
The only problem I have with saying ground speed is preserved is that "ground speed" is a meaningless term once you're airbourne - it's a speed as opposed to a velocity, with the direction determined by the ground. It's converted into its actual velocity when doing anything that isn't travelling along the ground. It's definitely worth mentioning that it protects from a single hit. Elemental shields are more specific, but I'd say the standard shield is as integral to the game as rings and lives are. Checkpoints aren't actually individual; each checkpoint has a number, and when you hit a checkpoint, that checkpoint and all checkpoints with a lower number are triggered and cannot be interacted with again. There are some exceptions to a complete reset, but they're not the norm. Sonic 1 8-bit's extra lives are collected permanently and don't respawn after death (most likely because of the special bonus you get for collecting every extra life). Though Sonic 1 8-bit also resets the timer to 1:30 when you respawn from a checkpoint (as opposed to the Mega Drive games saving the value the timer was when you hit the checkpoint), and probably wouldn't be considered a classic Sonic game for these purposes anyway. It may also be worth mentioning time overs - they act the same a losing a life but reset the time to 0:00 when you respawn at the checkpoint. Also bottomless pits probably need to be mentioned alongside crushing hazards as an insta-kill. The spike bug doesn't as that's a specific object property already covered by the vulnerability state thing.
So it's more accurate to say his current velocity is incorporated into the resulting vector from the jump or from him falling, probably? As well as talking about the air resistance when describing the air state; Yeah, that makes sense. It's a mechanic that prevents ring loss and can basically be described like that. Huh, I didn't know that! I knew they don't operate on hitboxes but on triggers, but that didn't matter that much for what's at stake here. I think it's worth not to generalize the time reset thing anyway because although it's consistent across all Mega Drive games and Sonic CD, there's nothing about setting it to 1:30 that turns the mechanic into something different (unlike the time over resetting the timer). I'm thinking of doing the same for as many instances involving numbers as possible, using them as examples rather than "enshrining" them in the rule. Absolutely, these were oversights and I'll incorporate them. Thanks a lot!
So after applying @DigitalDuck's corrections, adding points to underwater gameplay, Super gameplay and the camera, I think we have a functioning, if basic, theoretical general formulation of Classic Sonic gameplay. Of course, I'll always need you guys' criticism and input. So I hope this is at least a bit useful to at least some of you. Now why do this anyway? I think it's useful for a few things. First, it allows us to open dialogue with any other gameplay styles, including Sonic's modern and alternative ones, because they can be described using similar terms, and that allows any exchange -- critical or creative -- to be more fruitful. It's a general approach to comparisons we often make using "local" terms; Second, it allows us to analyze Sonic's classic gameplay without preconceived value judgements. Having all this doesn't make a "good Sonic game", but it helps us identify core aspects of this said gameplay style, which ones still persist, which ones were abandoned etc.; Third, it allows us to formulate some chains of causation. This is not the only way one could have worded any of this. You could start with what you see on the screen and go from there. You could start with the core mechanics and reach the objectives afterward. This is almost ideological, but the way I formulated subtly implies the core mechanics are at the core because they're what makes objectives possible. If you start from the core mechanics until you reach the objectives, you subtly imply they are more important. This distinction is absolutely huge, and a very important part of general formulations. This can help creatives select what they'd like to focus on when making new fangames and not stray from there, messing with the original rules more consciously. For a very basic example, people all say lives are an obsolete mechanic, even for classic Sonic, and will either do away or call for doing away with them. This formulation helps to see clearly what removing them means, how this affects progression and other gameplay mechanics. So it leads us to better informed opinions on how or why Classic Sonic as a whole, and not just one aspect or other, works. For another example, each and every rule here can be simply ignored or redacted. Sonic doesn't need to be teleported to his last checkpoint when dying (like shmups usually don't do), and objects don't need to not interact with each other in a stage. A badnik could be able to kill another badnik or collect ringss by themselves, why not? Knowing which rule you're subverting leads to a consistent approach to innovation to the gameplay. Of course, game design and developemnt is generally iterative and experimental, but this can help too!
The rules for every game should be on the wiki. Some of them will be, but lots fall through the net. I know historically there's been a lot of confusion over end of level bonuses, because sometimes they're impossible to obtain. Chaotix gives points if you end with an item (e.g. a shield, or the blue combine ring), but we didn't know that until I started investigating the prototypes a couple of years ago. But even that might be missing from the wiki because I was doing other things. Team work makes the dream work, etc.
It's important that you bring up Chaotix here because yeah, it's not the retention of rings that nets you points but the retention in general, which could theoretically extend to any items or effects. It just so happens that generally it only counts rings. I'm not sure laying out rules is too easy in the wiki as it is: while Sonic 1 mostly has them, many aren't there and the gameplay is described without a strict hierarchy (it describes objectives, mechanics and even the reason for their implementation in the same breath), which actually makes it more readable and even interesting. Still this right here also makes a good template for rules for each game being strictly described.
Would like to make some small corrections for Sonic 1; Every zone bar Scrap Brain Zone has a boss, and Final Zone’s boss only takes eight hits, not twelve. You were probably thinking of the Death Egg Robot from Sonic 2, which does indeed take twelve hits.
Labyrinth Zone's boss also functions differently to the others, as while you can defeat it by delivering eight hits, it isn't required and the screen never locks you in place. Instead Eggman will just run away once you reach the end.
You don't seem to account for Special Stages that take place after an act. There wouldn't be a stage to return to in those cases.
There should be a better way to word it, but even these do return you to the point you were in the general progression. It just so happens that this point is the liminal space between one stage and another, so nothing else happens.
