Single Player

A screenshot of Single Player gameplay.

Single Player is the main game mode and gametype in SRB2. It emulates the gameplay of the Genesis-era Sonic games, albeit in a 3D environment. The player steers a character through levels in a third-person view and must overcome several obstacles and challenges to reach the exit. An exception to this are boss levels, in which the objective is to fight and defeat a boss. Single Player mode is enabled for a map by adding the keyword Solo, SP, Singleplayer or Single to the TypeOfLevel parameter of its level header.

Unlike the other main gametypes, Single Player mode is not playable in netgames and can only be played with one person in general. An exception to this is when Single Player mode is played with a player and bot combination such as "Sonic & Tails", where the first player takes control of Sonic and a second player can optionally take control of Tails. However, Tails acts only as an assistant to the first player, contributing to Sonic's ring count and needing to be within range of the first player in order not to be respawned automatically. Cooperative mode (or Coop for short), meanwhile, is a fully multiplayer-compatible version of Single Player, where every player has individual statistics and do not have to depend on each other to play the game.

Level structure

SRB2's official Single Player levels are organized in zones: Each zone consists of three acts, of which the first two ones are regular levels with an exit sector and the third one is a boss fight. The only exception to this is Black Core Zone, where the first act is a race against Metal Sonic and the second and third acts are boss fights. Each zone has its own distinctive visual theme and gameplay style that sets it apart from other zones. Many custom levels follow this format, but it is not required. A zone can span between 1 and 19 acts, and it is also possible to remove "Zone" from a level's name altogether with the NoZone level header parameter. Boss fights may be omitted altogether or integrated directly into the regular levels.

Regular stages

In the zone format the official SRB2 levels use, the first and second act of each zone are regular Single Player stages. The player starts out at a Player 1 Start and has to progress to an exit sector, which typically contains a Signpost that spins once the player finishes the level. In between these two points, obstacles are located that the player has to pass. Additionally, each zone contains a distinctive roster of enemies that act as additional threats.

To increase replay value, the official SRB2 stages all contain multiple paths that the players can choose from and that contain different challenges. Additionally, hidden power-ups and other items are scattered throughout the stage and can be found by diverging from the pathway. Apart from power-up monitors, the official SRB2 stages also contain a varying number emerald tokens that, when collected, allow players to access the Special Stages after the level has ended and try to collect the Chaos Emeralds. Each stage also contains five emblems, which are small winged logos hidden in the stage. Collecting these unlocks secrets once the game is completed. Three additional emblems are awarded for beating certain requirements in Record Attack, one for each discipline.

Boss stages

In the zone format the official SRB2 levels use, the third act of each zone is a boss battle. These acts generally consist of small arenas in which the player has to fight Eggman in one of his machines. In SRB2's official boss levels, the arena contains no rings, but the player is awarded 10 rings automatically at the start of the stage. The amount of rings that are awarded can be configured with the StartRings level header parameter. SRB2's bosses take eight hits to defeat, except for Brak Eggman, who takes twelve. Generally, when the boss is defeated, an Egg Capsule will rise somewhere in the level. The level ends when the player hits the button of the capsule and releases the flickies inside it. Boss levels that end with an Egg Capsule do not need an exit sector. However, it is also possible to end a level directly upon beating a boss (by setting the Object Special flag on the boss Thing) or to trigger a dynamic event that allows the player to progress (via linedef executors using the reserved tags -3 and -4). The latter feature is used in Black Core Zone Act 2 and Act 3.

Other stages

Apart from these two main types of stages, there are some differently structured level types that are used in conjunction with other gametypes:

• NiGHTS stages do not have an exit sector, but rather an Ideya Drone where the player transforms into their NiGHTS form and flies along a NiGHTS track in 2D mode. These stages contain an Ideya Capture that the player must deposit rings in to destroy it and complete the level. Some Single Player NiGHTS levels may be explored freely in 3D mode without entering the NiGHTS track; setting the Ambush flag on the Ideya Drone removes that option.
• Special Stages are stages that allow the player to collect a Chaos Emerald. SRB2 supports two types of Special Stages: NiGHTS stages, and 3D stages in which the player has to collect a certain number of blue spheres in a specified time to obtain the emerald. The level header parameters SpecialStageTime and SpecialStageSpheres determine the time and sphere requirements for the latter type.
• Emerald Hunt stages do not have an exit sector, but rather contain three emeralds that the player, equipped with a radar, needs to find to complete the level. The emeralds appear randomly in three of the Emerald Hunt Location Things placed onto the map.

Gametype format

Save slots

When starting up a new Single Player game, players may choose a save slot (or choose to play without saving) and a character to play as. This character choice cannot be changed afterwards. The game automatically saves progress at the start of each level. For custom levels, the SaveGame level header parameter controls whether the game saves upon entering the level or not. Beating the last Single Player stage unlocks the Extras menu (if it isn't unlocked already) and turns the save slot into a level select. Unlike the unlockable level select, this level select forces players to use the character that was chosen for the save slot, but saves how many lives the player has instead of always starting out with three.

Lives and continues

Upon starting the first level, players are awarded with three lives and one continue. They will lose a life upon dying (getting hit without rings, getting crushed, falling into a pit, drowning or suffocating in space) and can collect additional lives by finding Extra Life Monitors, scoring 50,000 points (a life is awarded for each 50,000 points, so another life will be awarded after 100,000 points are reached, etc.), or collecting 100 rings in the current stage. Another extra life is awarded after collecting 200 rings, but not for collecting 300 rings and beyond. However, the MaxXtraLife parameter in the MainCfg block can be used to change this for addons.

Players who lose all their lives may choose to use a continue and respawn at the start of the current level. The number of lives they start out with increases with each used continue:

Used continues	Starting lives
0	3
1	5
2	7
3	9
4	12
5	15
6	20
7	25
8	30
9	40
10	50
11	75
12	99
13 and above	Infinite

Once a continue is used, it is removed from the save slot. An additional continue is awarded for each 50,000 points that are scored in a Special Stage. If the player already has all Chaos Emeralds, a continue is awarded for each collected emerald token. If a player reaches zero lives and zero continues, they will get a Game Over.

Points from enemies/bosses

Points can be scored during a level by destroying enemies. 100 points are awarded for every enemy destroyed, although more points are awarded if the player kills several enemies in one move, typically by bouncing off multiple enemies after a single jump. The score chain is broken if the player touches the ground or is climbing a wall (except when invincibility is in effect), resetting the points awarded to 100 each.

Number of enemies	Point value per enemy
1	100
2	200
3	500
4–14	1,000
15 and above	10,000

Furthermore, destroying a boss (such as the Egg Mobile) or collecting an emerald token will award the player an additional 1,000 points.

Score tally and bonuses

Once a level is finished, the score tally screen shows up and bonus points are awarded to the player before the next stage is started. This includes 100 points for every ring they carry at that moment, a time bonus depending on how long they took to complete the stage, and an additional perfect bonus worth 50,000 points if they collected all rings in the stage.

Time	Bonus (in points)
0:29 or less	50,000
0:30–0:59	10,000
1:00–1:29	5,000
1:30–1:59	4,000
2:00–2:59	3,000
3:00–3:59	2,000
4:00–4:59	1,000
5:00–5:59	500
6:00–6:59	400
7:00–7:59	300
8:00–8:59	200
9:00–9:59	100
10:00 and above	0

In boss levels, the time bonus is replaced with a guard bonus, awarding points depending on how many times the player was hit. Perfect bonuses are not awarded in boss levels.

Times hit	Bonus (in points)
0	10,000
1	5,000
2	1,000
3	500
4	100
5 and above	0

In NiGHTS levels, the bonuses are replaced with a score bonus and a lap bonus. The score bonus simply adds the score earned on the NiGHTS track to the player's overall score. The lap bonus awards 1,000 points for each additional lap the player completed around the track after destroying the Ideya Capture.

The BonusType parameter in the level header determines which types of bonuses are awarded in a level. The available options are None (no bonuses), Normal (ring, time and perfect bonus), Boss (ring and guard bonus), ERZ3 (ring, guard and perfect bonus), NiGHTSLink (score and lap bonus) and NiGHTSLink (link and lap bonus).

Cheats

Several cheats can be used in Single Player; however, they mark the game as modified to prevent the player from unlocking secrets while using cheats. Most of these cheats can be used by enabling the devmode console command, which is exclusive to Single Player. There are four exceptions to this:

• god makes the player invincible to everything.
• noclip makes the player intangible to all Objects and walls, allowing them to pass closed doors and reach the top of platforms immediately.
• notarget prevents enemies and bosses from targeting the player unless they are hit.
• objectplace enables a special debug mode where the player can fly around and place new Things in the map. For more information, see the Object placement mode article.

Other cheats include setting the number of rings, lives and continues the player is equipped with, creating a temporary Star Post to respawn at, getting all emeralds, teleporting, scaling the player, flipping the gravity and changing character attributes. For a full list, see the development mode article.

Co-op

Cooperative mode, generally referred to as Coop, is a fully multiplayer-compatible version of Single Player. It is mostly identical to Single Player, but can be played with multiple players simultaneously. A map can be given Coop support by adding the keyword Coop or Co-op to the TypeOfLevel parameter of its level header. This is normally advisable for Single Player levels, although mappers should take care that their map is Coop-compatible. Obstacles and hazards that would block the path for some players should be disabled (usually done by giving the linedef special the No Netgame flag).

A Coop stage usually ends when the first player has reached the exit. This behavior can be changed in the Options menu and with the playersforexit console variable. One is the default behavior, while All forces all players reach the exit for the stage to end. Emerald tokens can be collected as usual, and the number of Special Stages that are accessed after the level has ended depends on how many tokens all players have collected together. In the Special Stages, the ring and sphere counters are shared among all players, while the time limit is individual for each player.

An useful feature for Coop is Tails' ability to transport other players while flying, which can be enabled with the tailspickup console variable. This allows Tails players to transport Sonic and Knuckles players to places they couldn't normally reach or to help them bypass obstacles.