Sonic Robo Blast 2

Sonic Robo-Blast 2 (or SRB2 for short) is a free, fan-made Sonic the Hedgehog game using a modified version of the Doom engine, based on Doom Legacy (in Active Development since 1998). The game focuses on recreating the feel of the classic Sega Genesis games in 3D, as opposed to the newer styles that Sega has been making games for now. So far, the current release version is version 2.2.11. It is not yet complete, as some acts of zones are missing, and Dark City is only at its conceptual stage.

A common misconception regarding Sonic Robo-Blast 2 is that it is seen as a mod for Doom. However, SRB2 simply runs on the same engine as Doom, and you do not need to own a copy to play the game.

Gameplay
In SRB2, players run at high speeds through generally light-hearted levels (though some slight exceptions do exist, such as Castle Eggman Zone, Arid Canyon Zone, Red Volcano Zone, Egg Rock Zone.), in comparison to the usually dark, dim, and gritty environments of Doom levels. Players jump heights unprecedented in Doom, achieving heights of 124 fracunits. Players are additionally equipped with a spindash, which can be charged up using a spin button. Also, players encounter badniks in the field, that can be destroyed by jumping on them once, as opposed to the hellspawn of Doom which requires several shots to be slaughtered. After two acts of gameplay, players encounter a third act of gameplay in which they find a boss, who must be completed to finish the level. In boss acts, an egg capsule rises out of the ground for the player to jump on and finish the act. However, not all boss acts feature an egg capsule, and end the level shortly after defeated. The most current version of Sonic Robo Blast 2 has eight different zones, some still not yet complete (like Red Volcano Zone, which is supposed to get a second act in the near future.)

At the character select screen, players choose between one of six characters: Sonic, Tails, Knuckles, and the three secret characters, Amy, Fang, and Metal Sonic. While Tails and Knuckles have mid-air abilities that resemble their previous appearances (Flying and Climbing, respectively), Sonic has an ability not seen in previous Sonic games: the Speed Thok. When Sonic thoks, he shoots forward at high enough speeds to pass through one-sided linedefs. (Map designers have reacted by inventing the Thok Barrier, a dummy sector of height 0 which completely surrounds a level, permitting the boundary walls to be two-sided.) This gives Sonic a massive advantage in multiplayer modes such as race, and also in the single-player time attack.

Another feature of SRB2, special stages are included for the player to collect chaos emeralds. When the player finds an emerald token in the field, they will be taken to a special stage. Inside a special stage, the player must go through NiGHTS levels. There is a specified amount of Blue Spheres to collect. The player must collect the orbs and make it to the Egg Capsule, when the player breaks the capsule; they carry with them the Chaos Emerald. With the Emerald, the player must make it back to the starting position to beat the stage.

In multiplayer, these stages are changed to different special stages specifically for multiplayer in which players must also collect Blue Spheres, however, it is more reminiscent of Sonic 3 and ''Sonic 3 & Knuckle's Special stages, where the player will automatically obtain the Chaos Emerald upon collecting all the Blue Spheres. The player can also get a continue by collecting all the rings (shown in the upper right corner). It is said these stages are supposed to get reworked in a future update.''

After collecting all the Chaos Emeralds, Sonic obtains the ability to turn into Super Sonic. Players turn into their super form by doing their mid-air action with 50 rings and no shield. When the player is in his Super form, he can jump higher than before, as well as run faster, and on water. Sonic has the ability to float in mid-air when the player presses and holds the spin button in the air. While in Super Form, the player is constantly drained of rings. After the player loses all of their rings, the player turns back into their normal state, with normal jump height, speed, and loses the ability to run on water and float.

Multiplayer
Multiplayer is a set of gametypes in SRB2 that allow play for more than one person. Multiplayer games are either played split-screen on one computer, or over netgames, where one player hosts a game on a network using several computers, such as the Internet.

To join a netgame, there are four methods: When selecting the server browser for the first time in a session, the game will ask you which room to choose (Standard, Casual, Custom Gametypes, or All).
 * Go to the Multiplayer menu, and click on the "Join Game (Internet)" option. Any games hosted on the Master Server will be shown on a list. Select the one you want to join and hit Enter, and it will attempt to join.


 * Go to the Multiplayer menu, and click on the "Join Game (LAN)" option. Here you can select games hosted over your local network instead of the internet.


 * Go to the Multiplayer menu, and click on the "Join Game (IP Address)" option. Type in the IP address of the person hosting the game you want to join. This is used for private netgames that should not be displayed on the Master Server.


 * You can type  into the console. This method works in the same way the "Join Game (IP Address)" option does.

To host a netgame, there are several necessary procedures you must follow. First and foremost, you must have port 5029 UDP open. Once this is done, hosting your game is simple. Just go to the "Multiplayer" option in SRB2, select "Host Server" option, and choose your settings. If you want to advertise your game on the Master Server, choose the "Yes" option on "Advertise on internet". This will allow people to search for your game and join it. If you want the game private, select "No" on the "Advertise on internet" option, and only people who know your IP address and that you are hosting can join.

Modifications
SRB2's Engine is a heavily modified version of the DOOM Legacy Engine that supports many modification ways such as LUA Scripting, Floor over floors (FOFs). There are many existing modifications for Vanilla SRB2, but most aren't updated to work with the newest version of the game (2.2). Below are listed some of the mods for version 2.2.

Modifications (Larger PK3s and WADs for SRB2 2.2.X)

 * SRB2 Bomberman  (By Flame)
 * SRB2 Battle! (By CobaltBW)
 * SRB2 Tron  (By Flame )
 * SRB2 Prop Hunt (By Sharb)

Levelpack Addons for 2.2.X
Due to version 2.2's rework of the entire game, most modifications from version 2.1 aren't supported anymore. Listed below are some of the EXE and WAD mods for SRB2 2.0.X and SRB2 2.1.X.
 * Dimension Glaber  (By glaber)
 * The Cyberdime Realm (By Zeno)
 * Way Past Cool!  (By icykitsuu )
 * SRB2 Apologue Pack (By RomioTheBadass)
 * Blast Mania (By S1rexer)

Engine Side Modifications (EXE Mods for SRB2 2.0.X)

 * SRB2 Riders (By Chaos Zero 64)
 * SRB2 Community Blast (By Kalaron)
 * X-SRB2 (By Inuyasha)
 * Super SRB2 Kart-Z (By ZarroTsu)
 * SRB2 Plus (By Koopa badnik)
 * SRB2 CineBlast (By Cinefast )
 * SRB2 Morphed (By Morph)

Levelpack Addons (WADs Mods for 2.1.X)

 * Sweet Bro and Hella Jeff (By Boinciel)


 * Mystic Realm (By Mystic)


 * Tortured Planet (By Fawfulfan)

Levels
Below are all the current levels as of version 2.2.

Single-Player
Greenflower Zone - A grassy area filled with rivers, small trees, and flowers. Act 1 is a rather short level that introduces the player to the basics of the game. Act 2 takes place at the bottom of large canyons and also features large rivers, waterfalls, and caves. The boss of Greenflower Zone simply fires regularly-timed lasers in Phase 1, which becomes faster in Phase 2.

Techno Hill Zone - Eggman's presence in this area has altered the landscape. Most noticeably, he's filled low-lying areas with slime, which the player is now able to jump into since it is no longer harmful. The Slime will instead use an extremely buoyancy. Act 1 takes place outside and in the entrance to one of Eggman's factories. Act 2 takes place in the heart of the factory somewhere in the city during the night and has lasers, conveyor belts, crushers, and turrets. The boss flies in a circular pattern while spewing small puddles of slime. After 5 hits, the boss bounces at the player and spews slime into a circular pattern with each bounce.

Deep Sea Zone - As the name would imply, this zone is set largely underwater. Remain there for 15 seconds, and the player will drown. However, the countdown can be reset by grabbing large air bubbles as they emerge from the ground. Other hazards include collapsing ruins, waterslides, and underwater currents. In addition, there are puzzles involving pushable stone gargoyles, which often led to rewards. The boss here emerges from one of five chutes and tries to shoot the player with missiles, while also releasing a harmful electric field. After five hits, the boss makes clones of itself that also shoots at the player.

Castle Eggman Zone - Takes place in the rather gloomy medieval fortress under Eggman's care. Swings will propel you ahead and above, but watch out for swirling maces, cannonballs, and flamethrowers. Act 1 takes place in the outside of the structure, while Act 2 covers the chambers and grounds of the titular castle. The boss of Castle Eggman Zone swings around three arms of spike-balls around itself constantly. It is protected by a cage that opens up after activating switches, allowing the player to hit it. After five hits, the cage is destroyed and the boss then flies up high above the ground continuing to spin the arms, revealing springs hidden under the switches, which the player can use to reach the outer parts of the arena (taking care to avoid the spike-ball arms being swung around and the crowd off Eggrobos which fling you back into the arena), where the player must then must jump off the arena to hit the boss. Each time the boss is hit in this phase, the spike-ball arms will swing faster.

Arid Canyon Zone - This rather scenic and rugged canyon is accented with cacti, tumbleweeds, and the occasional oasis. Moving cables will give you a lift over the precarious ground. Jump quickly to escape quicksand and pools of oil. Watch out for rockslides, open fissures, and slippery oil slicks. Act 1 takes place in the desert canyons, while Act 2 will take you on minecarts and insides of the desert. The boss of Arid Canyon is Fang The Sniper, who will use bombs and his Pop Gun as attacks. After five hits, he will destroy the roof of the level, revealing that the location is a moving train. He will then begin leaving bombs on every jump and taking longer to become vulnerable. After defeating Fang he will be unlocked as a playable character.

Red Volcano Zone - The lava in this expansive subterranean cavern is prone to rising without warning, so watch out. Other things to be wary of include a series of collapsing platforms and jumping fireballs. Red Volcano Zone has one act and no boss.

Egg Rock Zone - The player finally makes it to Eggman's extraterrestrial headquarters planted firmly on the energy-filled Black Rock. This zone features many of the previous levels' hazards and gimmicks and adds inverted gravity (which can be triggered by the player sometimes and sometimes not), airlocks, and short romps through airless vacuums. Remain oxygen-free for too long, and you'll suffocate. Act 2 takes place even deeper in the base with 2 completely different split paths, more anti-gravity segments, more 2D segments, and even a mini-boss on one of the split paths. Egg Rock Zone has no Act 3, but Black Core Zone could be considered Egg Rock's boss, even though Egg Rock was originally planned to have a third act.

Black Core Zone - Act 1 is a race against Metal Sonic, where the player must get to Metal Sonic who is sucking the air out of the stage, killing the player if he gets to the end. Act 2 is a battle against him, where Metal Sonic has four different usual attacks such as the small orbs, large orb, three large orbs, and dash attack. After 5 hits, he gets on his pinch phrase and uses a dash attack on the player. Act 3 is the final act of the game, where the player is in the final showdown against Black Eggman, who acts similar to the Cyberdemon along with also using a flamethrower. This boss is covered by electrical barriers and in order to stop the barriers, the player must lure the boss into the acid fall and after that, the player will be able to hit the boss. After 9 hits, the walls of the arena will crumble, rendering his missile attack more potent. After the boss is defeated, the level is completed and you then go to the credits. Completing the game also unlocks Metal Sonic as a playable character and Haunted Heights Zone.

Secret Levels
​​​​​Frozen Hillside Zone - A hidden level unlocked after collecting 5 emblems. Frozen Hillside is covered in snow that slows you down upon walking in it, icy terrain, and snow avalanches. At the end of the level, you will find Amy Rose, who will be unlocked as a playable character after finishing the stage.

Pipe Towers Zone - A tribute to the original Super Mario Brothers, with 16-bit Goombas, Koopa shells, coins, and item-filled boxes. This level is unlocked after collecting 20 emblems. The level has 2 areas, of which  Area 1 is the overworld while Area 2 is the underworld. It is somewhat large and includes Mario enemies and items.

Forest Fortress Zone - A tribute to the original Castle Eggman Zone from version 2.1. This level is unlocked after collecting 60 emblems. Forest Fortress Zone will have you running through an endless array of spike-balls, maces, and Lance-a-bots.

Techno Legacy Zone - As the name implies, this is the original stage concept for Techno Hill Act 2, all the way from 2.0. This level is unlocked after collecting 100 emblems. The level features harmful acid water, lasers, and Detons. It is also the only level in the game that uses the Crawla Commander badnik.

Christmas Chime Zone - A delightfully abstract winter-styled landscape with reduced gravity. Unlike the other NiGHTS stages, running out of time here will not end the stage, and will allow you to run through the stage at the cost of losing all your points. One of the emblems in this stage requires the usage of this mechanic due to not being able to reach the emblem in the Super Form. This level was previously known in version 2.1 as ''Spring Hill Zone. ''

Dream Hill Zone - A big, open, and 3D NiGHTS stage. Although the stage does not use the 3D aspect to it's fullest, it allows you to explore the stage and collect additional Blue Spheres before transforming into Super Sonic. Unlike the other NiGHTS stages, this stage has multiple mares, each with individual rankings. This level is unlocked after beating the game with all the Chaos Emeralds.

Alpine Paradise Zone - A NiGHTS zone with the same mechanic as Dream Hill Zone, allowing you to traverse the level in 3D before transforming into Super Sonic. This is the only zone of the bonus acts to have 2 acts and it is also the only NiGHTS zone to have 2 acts. The first act is unlocked by getting a C rank (or higher) in all the special stages, and the second act is unlocked by getting a B rank (or higher) in all the special stages.

Black Hole Zone - The eighth special stage. This stage is considered by many to be the hardest to obtain and the hardest to beat. The level is unlocked by getting an A rank in all the previous special stages (excluding bonus NiGHTS levels). This stage is unforgiving, with a strict timer and requirement of 150 blue spheres, endless amounts of crushers, and 2 of the hardest emblems in the entire game.

While the previous levels are unlocked by collecting Emblems (or getting ranks in NiGHTS stages), the next are Challenge Levels which unlock one by one after finishing the unlocked levels.

Haunted Heights Zone - A hidden level styled after Pumpkin Hill from Sonic Adventure 2. This level is unlocked after beating the game. It features ghosts, the Techno Hill slime, a lot of conveyors, and bottomless pits. The level also features an enemy called Cacolantern, which is a reference to the DOOM enemy Cacodemon.

Aerial Garden Zone - A hidden level set on a picturesque floating temple. This level is unlocked after beating Haunted Heights Zone. The name of the game here is risky platforming over an unforgivable and vast bottomless pit. Activate panels (some of which must be warped to) to open doors and progress further.

Azure Temple Zone - A hidden level unlocked after Aerial Garden Zone is beaten. Azure Temple Zone features bottomless pits along with tight platforming. The player is constantly underwater, which means they have to be mindful of the air bubbles scattered about.

Gamemodes
SRB2 supports numerous multiplayer modes, some of them sporting first-person gameplay, while others featuring more Sonic-like gameplay.

Co-op
SRB2 supports a Cooperative mode, in which many players can complete a level together. The levels proceed normally, and after one player completes the level, the stage ends (This can, however, be changed in the netgame settings to require one-fourth, half, three-fourths, or all players to finish).

Race
(Circuit levels have been removed from the game as of version 2.1.X, the gametype still exist, however.) There are two types of race modes: Competition, and Race. Competition is played on single-player levels, the categories in which points are awarded are the same, but points are not only awarded for winning a category. Instead, for each category, the highest-ranking player receives the maximum amount of points while each successive player receives one point less up until the lowest-ranking player receives no points. This is done for all categories and the resulting points are combined to form the score. This significantly reduces the chance of ties in games with more than two players. 60 seconds after the first player finishes, all players that have not finished run out of time and die. As for completing the levels, two systems exist: normal and circuit. The normal racing method simply consists of racing through Co-Op levels that have an exit. The circuit racing method gears toward completing multiple laps of a track, the number of which is defined by the server.

Match / Team Match
Players chuck rings at each other. Rings draw ammo from the player's ring count, and thus the player must conserve ammunition. Also, an interesting twist is that a player loses all of his rings (which are also ammo) after being hit. The player is given invincibility time to collect spilled rings or just plain rings. When the match ends, the player with the most points wins. As of version 2.0, a new Match system has been coded, along with Tails and Knuckles' super form, only available in Match or CTF. However, Team Match is a variation of Match and it features players being divided into two competing teams that fight each other.

Tag / Hide and Seek
These two similar game modes both feature tagging other players, whether it be firing rings at the untagged players, or even touching another player, should Touch Tag be turned on. While untagged, players will be awarded score at a constant rate per second as a reward for remaining untagged, but will no longer gain this upon being tagged. Tagged players will gain 100 points for tagging another player, as well. The main difference between Tag and Hide and Seek is that in Tag, players will become IT once they get tagged, with the round ending once every player is tagged, while in Hide and Seek, players are not given the IT status, and cannot move once being found, with the game ending once all players are found. The game may also end if the time limit or point limit is reached first.

Capture the flag
In Capture the Flag, players attempt to capture the opposing team's flag. Players choose teams by selecting a team in the menu screen, or by entering Changeteam "Red", "Blue" or "Spectator" in the console. Both flags must be at the base to score a point. Also notable, the player loses the use of his mid-air ability when carrying the flag.

How to load add-ons
New characters and levels and many other modifications can be added by opening the Addons menu on the title screen and selecting the file they want to load. Another way of adding mods is by entering the console (by pressing the key ¬ or `) and typing the following without the quotes: "ADDFILE NAME.WAD" and then simply pressing enter to load the file in question.