Sonic Robo Blast 2


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Title screen of Sonic Robo Blast 2

Sonic Robo Blast 2 (or SRB2 for short) is a fan made, freeware Sonic the Hedgehog fan game using a modified version of the Doom engine, based on Doom Legacy. The game focuses on recreating the feel of the classic 2D Sonic games. As of 2023, the latest version of the game is version 2.2.13. It is not yet complete, as some acts of zones are missing, and development is still underway.


While the engine is derived from Doom Legacy, which was originally chosen for its 3D floors and support for deep water, it has greatly diverged and expanded in a different direction.

  • The original Doom games are no longer supported. FraggleScript has been removed as well.
  • New 3D floor types (called FOFs, or "floors-over-floors" in the SRB2 community), such as intangible from one side, crumbling a few seconds after a player lands on them, 3D water with its own physics, player-slowing quicksand, blocks that can be "busted" into rubble, and custom 3D Floors allowing combination of built-in 3D Floor effects, among others.
  • Polyobjects with additional effects allowing to create moving platforms. They can now render flats, carry players standing on them, follow waypoints, and can have sector specials applied to them.
  • Lua scripting
  • Custom "SOC" (Sonic Object Configuration) content definition language
  • Partial support for ZDoom's TEXTURES lump
  • Camera effects
  • Skins extended to full-fledged character classes with the potential for custom abilities
  • Slopes with Classic Sonic styled physics. 3D floor slopes, vertex-based slopes and dynamic slopes are all supported in both Software and OpenGL Renderers.
  • Reverse gravity and Scale actors ingame, works on both Software and OpenGL Renderers.
  • v2.1.21 added PK3 support to help reduce file size and improve organization of resources through subfolders.
  • v2.2.11 added UDMF support and removed the framerate limit of 35 fps.


In SRB2, players run at high speeds through wide and distinct locations, from bright green hills like Greenflower Zone to solid, gloomy fortresses like Castle Eggman, in comparison to the usually dark and narrow battlefields of Doom levels. Players jump at heights unprecedented in Doom, achieving heights of 124 fracunits. Depending on the character, players can be additionally equipped with a spindash, which can be charged up using the spin button. Players encounter badniks in the field, that can be destroyed by jumping on them once, as opposed to the hellspawn of Doom which require several shots to be slaughtered. After two "acts" in most of the stages, players encounter a third act in which they find a boss, who must be defeated to finish the level. In most boss acts, an Egg Capsule rises out of the ground for the player to jump on to complete it. However, not all boss acts feature one, with the bosses ending the level shortly after defeat. The latest version of Sonic Robo Blast 2 has seven different zones, though some still not yet complete.

At the character select screen, players choose between one of three characters: Sonic, Tails, or Knuckles. While Tails and Knuckles have mid-air abilities that resemble their previous appearances (Flying and Gliding/Climbing, respectively), Sonic has an ability reminiscent to the Jump Dash in Sonic games: the thok, named after the sound it makes. Upon using the ability, Sonic shoots forward with a massive burst of speed. This gives Sonic a massive advantage in multiplayer modes such as race, and also in single-player time attack, although he sometimes has to take the long way around in steep levels. In addition to the main three, there are three additional characters with unique abilities like a melee weapon, a popgun, and the ability to dash through obstacles at high speed, each originating in other classic Sonic games, and each unlocked after beating certain stages.

In addition, special stages are included which allow the player to collect Chaos Emeralds. When the player finds an emerald token in a level, they will be taken to a special stage after finishing the level. The special stages are based on the gameplay of Nights into Dreams, in which the player flies along a curved 2D track and has to collect a certain number of blue spheres and finish the stage before time runs out to obtain an Emerald.

After collecting all the Chaos Emeralds, Sonic, Knuckles, or one of the unlockable characters obtain the ability to turn into Super Sonic. Players turn into their super form by using their mid-air ability with 50 rings and no shield. When the player is in their Super form, they can jump higher than before, as well as run faster, even skimming over water. Sonic has the ability to float in mid-air when the player presses and holds the spin button in air, and Knuckles makes the ground shake when he glides into a wall. 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 their special abilities.


These levels are current as of v2.2.13.


Greenflower Zone - A grassy area filled with rivers, small trees, and flowers. Act 1 is a rather short level which 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. Eggman's machine in the boss act of Greenflower Zone simply fires lasers at the player. After five hits, he will spawn 3 lasers at once instead of 1 at a faster rate.

Techno Hill Zone - Eggman's presence in this area has altered the landscape. Most noticeably, he's filled low lying areas with buoyant slime, which will cause the player to move slowly, and anything that enters it is slowly pushed back upwards towards the surface, which can be used to the player's advantage to be flung. 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 and has lasers, conveyor belts, crushers and turrets. The boss flies in a circular pattern while spewing small puddles of slime. After five hits, the boss bounces at the player and spews slime into a circular pattern with each bounce, and attempts to stomp the player.

Deep Sea Zone - As the name would imply, this zone is set largely underwater. The player may drown if they stay underwater for too long and ignore the warnings. However, the air timer 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. If the player falls into the water below, they'll be electrified a short time later. After five hits, invulnerable, inflatable Eggman clones will appear and start emerging from the chutes simultaneously, and will shoot at you along with the original.

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 forests and gardens on the property, while Act 2 covers the chambers and grounds of the titular castle. Its boss has a 3D floor based cage that it uses to protect itself while swinging around long strings of maces to hit you, while you press buttons to expose Eggman's capsule.

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 precarious ground. The player has to avoid cacti and TNT, all while proceeding with caution due to large puddles of oil, and riding minecarts along unfinished tracks. Beating the boss unlocks the first unlockable character.

Red Volcano Zone - The lava in this prehistoric volcano is everywhere, and it eats rings, so watch out. The player can ride stone spheres across it to get from place to place, though. Other things to be wary of include series of collapsing platforms and sudden lavafalls. 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), air locks, and short sections in airless vacuums. Remain oxygen-free for too long, and you'll suffocate. Act 2 is also features brief 2D sections, taking advantage of the "2D mode" exclusive to this game that makes it more akin to the classic Sonic experience. It's a marathon zone and has a considerable difficulty spike, which has been claimed to be due to the absence of the two not-yet-finished zones of Dark City and Grand Eggship.

Black Core Zone - Includes a race and fight with Metal Sonic, and a fight against "Black Eggman", a huge mecha that was based on still-present cyberdemon code, firing rockets and flames at the player in a similar manner. Beating the game will allow you to play as the second unlockable character.

Pipe Towers Zone - A tribute to the original Super Mario Brothers, with Goombas, Koopa shells, coins, and item-filled boxes. The first half of the level takes place in the overworld and through systems of pipes and bouncy mushrooms, and the second half is based off of the underground levels with moving platforms and Thwomps. The level ends with a 3D recreation of the end-level castle. Pipe Towers Zone has one act and no boss.

Haunted Heights Zone - The first challenge stage, which is unlocked by completing the main story. This industrial Halloween themed level adds several new thematically appropriate gimmicks such as player slowing spider webs and themed enemies such as a pumpkin shooting Cacodemon robot. Haunted Heights Zone features one act and no boss.

Frozen Hillside Zone - A series of snowy, ice cold valleys separated by caves, featuring hazards like pits of deep snow that make it difficult to jump, items encased in ice, and deep, frozen lakes. This zone consists of one act and no boss, and features a cameo from the third unlockable character at the end, who then becomes playable.

Aerial Garden Zone - A challenge level set on a grand floating temple. This level is unlocked by beating Haunted Heights Zone, the first challenge level. The name of the game here is risky precision platforming over a vast, unforgiving bottomless pit. Activate panels (some of which must be warped to) to open doors and progress further. Aerial Garden Zone originally had four acts and was part of a modification for an earlier version created by a developer for the game, with every act apart from the boss being combined into one to test the limits of the engine. The stage is sometimes contentious for its immense hazards and marathon length that can set you back all the way to the beginning if you make too many mistakes, so some just cheese it with Tails and Knuckles.

Azure Temple Zone - Another challenge level, Azure Temple Zone is set entirely underwater and is unlocked by beating Aerial Garden Zone. Your character moves slower in water, and combined with the tense air management and the arrow-spitting gargoyles, the narrow platforms can be immensely challenging. Azure Temple Zone features one act and no boss.

The game is still very much being developed, with the missing stages, revamps for the older ones, and even major gameplay changes like a physics overhaul being planned.


SRB2 supports numerous multiplayer modes, some of them sporting first-person shooter gameplay like Capture the Flag and Ringslinger Match, while others featuring more Sonic-like gameplay like Race and Co-op. There exists an online mode based off Doomseeker's method of a master server, with it also possible to host servers independently, as well as a 2-player Sonic the Hedgehog 2 split-screen style mode with no multiple PC nor server requirements.


SRB2 supports a Cooperative mode, in which many players can complete a level together. The levels proceed normally, and after one player (or all, depending on settings) completes the level, the stage ends.


This mode is a variation of Sonic 2's multiplayer split-screen mechanics. There are five different requirements: score, time, ring count upon finishing the map, total number of collected rings and number of popped monitors. Players receive points based on how well they were in each of the five categories (e.g. the player with the most total number of collected rings receives points equal to the number of players currently playing). The winner is based upon who has the most overall points at the end of the level.


In this mode the winner is based upon who finishes first, or Time is the only factor counted for the winner, as opposed to the points system installed in Competition. 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 first type of racing is much like any typical race: the first one to finish wins. The other type, circuit, requires the player to finish a number of laps around a course. The number of laps is specified by the server.


Players chuck rings at each other. Rings draw ammo from the player's ring count, and thus the player must conserve ammunition because it's very easy to fire until you have no Rings to protect you. Due to being a Sonic game, the player will lose both their ammo and their protection upon being hit once, unless they have a shield. When the match ends, the player with the most points wins. In addition to the traditional kind, there are special rings with different attributes, like rapid-firing Automatic, Spread, explosive Bombs and Grenades, Bounce, hitscan-style Rail, and Infinite Rings, which allow you to fire without drawing from your own ring stack until you run out. "Weapon panels" must be collected to unlock weapons, similar to guns in Doom, before the ammo for them can be used.


Players either shoot rings at each other or touch each other to pass on the "it" status. Characters who are not "it" lose their special jumping ability in order to give the person who is "it" a fair advantage. Points are earned if one player can avoid being tagged if the "it" status is given to another player. An additional variant of this game mode called Hide and Seek exists as well, which stops non-"it" players from moving after a set period of time and blinds the "it" player while the others hide.

Capture the flag[edit]

In Capture the Flag, players attempt to capture the opponent team's flag. Players are assigned to teams automatically after exiting spectate, and can also switch mid-game. Both flags must be at a base in order to score a point. The player loses use of their mid-air ability when carrying the flag.

Modding and add-ons[edit]

Sonic Robo Blast 2 has accumulated a substantial community, which is dedicated to creating several add-ons for the game. Custom maps are generally created using an editor called Zone Builder, itself a fork of GZDoom Builder. Due to SRB2's origins as a fork of Doom Legacy, many aspects of level building will be immediately familiar to Doom mappers. The game has Lua support, and a language for a file type called Sonic Object Configuration, or SOC. The formats used are .soc and .lua, as well as .wad and .pk3.

Addons can be loaded by entering the console (by pressing the key ¬ or `) and typing the following without the quotes: "ADDFILE EXAMPLE.WAD". Since 2.1, addons can be loaded in a GUI from the title screen, and since 2.2.12, they can also be loaded mid-game from the pause menu. Since that same version, they aren't considered by the game as "cheating" if you load them from the title screen, allowing you to gain unlockables or emblems with mods loaded and save your progress in a modified game.

See also[edit]

External links[edit]

Source code genealogy
Based on Name Base for
Doom Legacy Sonic Robo Blast 2 Sonic Robo Blast 2 Kart