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The '''Retro Engine''', also known as '''RSDK''', is a game engine created by "[[The Taxman]]" (Christian Whitehead). It is designed to deliver features from the 32-bit console era and below, and focuses on things like raster effects, palette manipulations, 'mode 7', and other features of retro games from back then, unlike modern engines today. The engine is multi-platform, and it fully supports modern essentials such as widescreen and online functionality.

==Engine==
The engine contains several features built for creating 2D titles, including collision systems, palette manipulation, loading of graphics via sprite sheets, and saving save data in custom binary files. Version 1 of the engine has a scripting language called TaxReceipt. Versions 2 through 4 have a scripting language dubbed "RetroScript" by the community. Version 5 of the engine contains RetroScript, but as a language transpilable to C, which gets compiled as a dynamically linked library that communicates with the engine. The engine stores all of the game data, including sprite sheets, metadata files, and RetroScript scripts/bytecode, in an (encrypted) archive file, with a .bin extension for v2, and a .rsdk extension for v3 onward.

==History==
The origins of the Retro Engine date back to the early 2000s, where it came to fruition out of the [[sonic:Retro Sonic|Retro Sonic]] project, by The Taxman, out of a need to have a more performant engine than Multimedia Fusion. This earliest version was written in Visual Basic, and released as the engine that the 2002 demo of Retro Sonic ran on. After the release of that demo, the engine was moved over to C++. After a development hiatus of over a year, this original version was scrapped, and the engine was rewritten from the ground up. 

In 2008, The Taxman joined Nexus Team, and subsequently, [[sonic:Sonic Nexus|Sonic Nexus]], the game they were working on, was developed for his new Retro Engine v2 (RSDKv2). In 2011, Nexus was intended to be merged with [[sonic:Sonic XG|Sonic XG]] and [[sonic:Retro Sonic|Retro Sonic]] to form [[sonic:Retro Sonic Nexus|Retro Sonic Nexus]], which would have also ran on Retro Engine. However, due to professional endeavors that the Taxman was working on at the time, these plans fell through and the merged project was shelved indefinitely.

Those professional endeavors turned out to be [[Sonic the Hedgehog CD (2011)|''Sonic the Hedgehog CD (2011)'']] for Xbox Live Arcade, PlayStation Network, iOS, and Android, which was developed by The Taxman and [[Stealth]] (Simon Thomley). This remake ran on a 3rd revision of Retro Engine ('''RSDKv3''').

Those ports were so successful, that The Taxman and Stealth were commissioned to do two more remasters in 2013: [[Sonic the Hedgehog (2013)|''Sonic the Hedgehog (2013)'']], and [[Sonic the Hedgehog 2 (2013)|''Sonic the Hedgehog 2 (2013)'']], for iOS and Android. These remasters both run on Retro Engine v4 ('''RSDKv4'''). 

Whitehead was approached by Sabrina “Strife” DiDuro, one of the developers behind [[wikipedia:Freedom Planet|Freedom Planet]], about possibly porting their game to RSDKv4, so that the game could run on consoles. A small proof of concept demo for this was made, but plans for the port fell through, as another, simpler way to get the game to consoles was found shortly thereafter.

In 2016, ''[[Sonic Mania]]'', another Retro Engine-powered game, was announced, and fully released in 2017, running on a new and much more feature rich, Retro Engine v5 ('''RSDKv5'''). In late 2018, with Christian joining the new game studio known as [https://eveningstar.studio/ Evening Star], it was decided to rename the Retro Engine and its RSDK format to the '''Star Engine''' and the '''Star SDK''' respectively.{{ref|https://eveningstar.studio/tech.html}} However, this decision was eventually reversed, as Star Engine developed and became a separate, 3D focused engine, for the studio to use for their title [[wikipedia:Penny's Big Breakaway|Penny's Big Breakaway]]. Retro Engine currently is still the copyright of Evening Star and Christian Whitehead.

In June of 2022, ''[[Sonic Origins]]'' was announced. It is a compilation that contains all the remakes of Sonic 1, 2, and CD, as well as a new remake of Sonic 3 & Knuckles. All of these titles run in a new iteration of RSDKv5, dubbed Retro Engine v5 Ultimate, or '''RSDKv5U'''. This is a specially modified version of RSDKv5 that contains backwards compatibility with both Retro Engine v3 and Retro Engine v4, allowing the Sonic CD, Sonic 1, and Sonic 2 to run with minimal modifications. However, despite that, modifications were still made to the titles, such as removing audio (audio is played through Hedgehog Engine 2, which the menus of the compilation run in) and adding new content, including the ability to play as Amy in all the titles, and Knuckles in Sonic CD.


==Decompilations==

In January of 2021, Retro Engine v3 and v4, and the games they were used for, were completely reverse engineered. The user [https://forums.sonicretro.org/index.php?members/rubberduckycooly.24911/ Rubberduckycooly] released two projects on GitHub: one of [https://github.com/RSDKModding/RSDKv4-Decompilation RSDKv4], for Sonic 1 and 2, and the other, [https://github.com/RSDKModding/RSDKv3-Decompilation RSDKv3], for Sonic CD. At the time, there were no plans for Sonic Mania to be also decompiled, due to the game's steep complexity compared to previous releases.{{ref|https://github.com/Rubberduckycooly/Sonic-CD-11-Decompilation#q-will-you-do-a-decompilation-for-sonic-mania}}

However, in August 2022, despite the previous statement, decompilations for ''[https://github.com/Rubberduckycooly/Sonic-Mania-Decompilation Sonic Mania]'' and its accompanying revision of Retro Engine, [https://github.com/Rubberduckycooly/RSDKv5-Decompilation RSDKv5], were released. Later on, RSDKv5U was also reverse engineered and added to the RSDKv5 decompilation repository.

These decompilation projects have allowed for non-official ports of the various RSDK revisions, and the games they run, for platforms such as PS Vita, Wii U, and 3DS, as well as furthering the development of modding/development tools for the engines. All the decompilations also feature a built in mod API, so no external mod loader is required. Any users looking to use these decompilations to play RSDK titles are still required to obtain a copy of the game's data through official sources, such as Google Play, the Apple App Store, or Steam. Furthermore, while pre-built binaries are hosted on the release pages of the decompilations, access to 
''Sonic Mania Plus'' or ''Sonic Origins Plus'' content in those releases is disabled, and is restricted to self-compiling the binaries, as a countermeasure to the decompilations possibly being used as a means to illegitimately play the aforementioned DLCs.{{ref|1=https://github.com/RSDKModding/RSDKv3-Decompilation/blob/master/LICENSE.md?plain=1#L10-L14}}

Most up to date news can be checked on the [https://forums.sonicretro.org/index.php?threads/sonic-1-2-and-cd-remake-decompilation.39890/ dedicated thread] in the Sonic Retro's forums.

==Games utilising the Retro Engine==
===[[Windows PC]]===
{{BulletPointGameList|category=Windows PC games using the Retro Engine}}

===[[PlayStation 3]]===
{{BulletPointGameList|category=PlayStation 3 games using the Retro Engine}}

===[[PlayStation 4]]===
{{BulletPointGameList|category=PlayStation 4 games using the Retro Engine}}

===[[PlayStation 5]]===
{{BulletPointGameList|category=PlayStation 5 games using the Retro Engine}}

===[[Xbox 360]]===
{{BulletPointGameList|category=Xbox 360 games using the Retro Engine}}

===[[Xbox One]]===
{{BulletPointGameList|category=Xbox One games using the Retro Engine}}

===[[Nintendo Switch]]===
{{BulletPointGameList|category=Nintendo Switch games using the Retro Engine}}

===[[iOS]]===
{{BulletPointGameList|category=iOS games using the Retro Engine}}

===[[Android]]===
{{BulletPointGameList|category=Android games using the Retro Engine}}

===[[Windows Phone 7]]===
{{BulletPointGameList|category=Windows Phone 7 games using the Retro Engine}}

===[[Ouya]]===
{{BulletPointGameList|category=Ouya games using the Retro Engine}}

===[[Apple TV]]===
{{BulletPointGameList|category=Apple TV games using the Retro Engine}}

==References==
<references/>

[[Category:Middleware]]