Sonic 2 v0.8.1 - Online party Options fix

The online Options screen now offers the enhanced party menu: choose up to four slots and play with Sonic, Tails, Knuckles, and Amy. Earlier netplay builds bypassed this menu and showed the original screen.

Roster and menu state now rewind with rollback. Applying a roster online affects the current session and preserves everyone's saved local settings. This patch includes the v0.8.0-rc2 startup fix.

Playing together

1. Everyone downloads and extracts the same v0.8.1 Windows ZIP below and supplies their own Sonic 2 Rev A ROM.
2. Before creating/joining the room, enable the desired character features under Mods. Amy requires Amy in Sonic 2 Rev 1.7.1; Knuckles requires the combined Sonic 3 & Knuckles donor. Each participant needs the donors for the host's enabled features.
3. Leave Sonic 3-style Save Menu disabled for netplay. Its toggle is separate from Knuckles.
4. Start the online match, open Options, set PLAYERS to 4, choose the characters, and press Start to apply. Each participant uses their player-1 controls for their assigned seat. Online lobbies support four participants; LAN/Direct IP supports two.

No game ROMs, donor ROMs, personal settings, or saves are included. Keep the assets folder beside the executable. Quickstates from earlier builds are incompatible; campaign SRAM remains portable.

Validated the exact ZIP with a two-peer session selecting all four characters through online Options, plus Knuckles/Amy gameplay and a rematch with forced rollback and simulated latency. Peers stayed in sync and local settings were unchanged. The Windows Release build and all three focused menu/party/character tests passed.

The final Internet playtest with these character selections remains yours to confirm.

Sonic 2 v0.8.0-rc2 — netplay startup fix

Fixes both peers closing when the host starts an online Sonic 2 match. The lobby was sending an empty game configuration before startup; it now publishes the host's current roster and video settings.

Everyone must use this rc2 ZIP. Extract it into a new folder, keep its assets and SDL2.dll together, and select your own Sonic 2 REV01 ROM. Host/join through Online as before. No ROM is included.

Validated on Windows with local online relay sessions, repeated matches, four players, differing local preferences, and forced rollback under simulated latency and packet loss. Confirmed state hashes matched with no desyncs. This is a playtest prerelease; the final Internet session with another person is still pending.

Local checks automate the launcher's lobby callbacks before machine initialization. They do not automate the graphical widgets or validate external relay deployment or donor-backed characters.

Sonic 2 v0.8.0-rc1 - Windows rollback netplay playtest

Superseded by v0.8.0-rc2, which fixes both peers closing on online match launch. Use rc2 for multiplayer.

Windows x64 playtest build for Sonic 2 rollback netplay, with up to four players and spectators online.

Download the ZIP below, extract it, and send the same ZIP to everyone playing. Each player supplies their own Sonic the Hedgehog 2 (World), Rev A / REV01 ROM. Windows needs the Microsoft Visual C++ x64 runtime, as with previous builds.

1. Start the executable and select your ROM.
2. For a party, the host first sets the roster in the game's offline Options and saves it, then reopens the launcher. Leave Sonic 3-style Save Menu disabled. Everyone needs the corresponding owner ROMs for any donor-backed characters selected.
3. Open Netplay > Online Netplay, create/join the same room, assign seats and start. Each participant uses their player-1 controller bindings for their assigned seat. Online rooms support up to four players; LAN / Direct IP currently supports two.

The host's roster and session settings are synchronized. Quickstates, turbo and execution-control scripts are unavailable during online play.

Validation: built with MSVC 19.41, netplay/rollback/ICE enabled and developer tracing disabled. A hidden 300-frame startup check passed with zero dispatch misses. Fixed the Windows clock portability errors and a missing callback symbol in stripped builds. Broader Linux QA is documented in the merged engine PR #12. Internet multiplayer playtesting is still pending; this is a prerelease for that test.

Source: game merge 697ad43; engine d80fb3f (included in engine merge 8157a8a); recomp-net 588059c; recomp-ui b9ef2f5. No ROMs or saves are included.

Sonic 2 v0.7.0 - Quickstates, visual saves and Super forms

Sonic 2 v0.7.0 adds complete local-party quickstates, visual campaign cards and Super forms for every Player 1 character.

• Save/load slots 1–9 through Escape > Save states, Shift+F1…F9 and F1…F9. Restore party, campaign session, video and audio at safe native boundaries, including pause and special stages.
• Campaign cards show owner-ROM-derived images for all 20 acts, numbered zones, CLEAR/static presentation, all collected Emeralds, and checkpoint lives/continues. Version-1 campaign saves remain compatible.
• Sonic, Tails, Amy and Knuckles can go Super as Player 1 with seven Emeralds and 50+ rings: hold jump through the apex. Keep each character's identity and abilities, native ring drain and reversion. Knuckles' Super palette comes from the supplied S3&K ROM.
• Add Sonic 3-style save-menu navigation feedback through Sonic 2's native sound driver.
• Keep P3/P4 closer to the leader, remove blocking legacy frame logging from normal play, and fix imported-companion rendering during Player 1 death.
• Game-specific implementation, configuration, disassembly and tests now live in the Sonic 2 repository. This follow-up changes no shared-engine code.

Party/campaign/quickstate features remain local-only. Special stages always use stock Sonic and Tails; native VS respects selected characters but does not gain Super. No Hyper forms or Super Flickies are added.

Windows x64: extract the ZIP and run SonicTheHedgehog2Recomp.exe, keeping assets/ beside it. Supply your own Sonic 2 (World) Rev A / REV01 ROM, and optional Amy Rev 1.7.1 / combined S3&K donor ROMs under Mods. No ROMs, extracted donor assets, settings or saves are included.

Campaign SRAM is portable. Machine quickstates require the matching build and mod/character/video setup: keep older states with their old executable; do not overwrite your previous installation without a backup.

Owner accepted gameplay and menu changes. Pre-release validation: 25 CTests, 60 Super fixtures, 36 campaign cases, 23 quickstate cases, and native before/after menu-audio comparison, with no dispatch errors. This is not exhaustive whole-campaign or four-controller certification.

Source: https://github.com/mstan/SonicTheHedgehog2Recomp (tag v0.7.0). PolyForm Noncommercial 1.0.0; third-party notices included.

Sonic 2 v0.6.1 - Companion and Knuckles animation fixes

Sonic 2 v0.6.1 fixes companion behavior and character rendering during local party play.

• Companions use native Player 2 recovery logic to return safely when left behind.
• CPU Players 3 and 4 have small deterministic differences in following distance and timing, so they spread out naturally. Player 2 retains its native behavior.
• Stable character frames and expanded sprite rendering remove party sprite dropouts and missing head/body streaks.
• Knuckles uses the correct standing/running poses and animation timing on slopes and loops.

The optional Sonic 3-style save menu, Campaign SRAM picker, local party options, and adaptive widescreen remain available. Existing campaign saves continue to work.

Windows x64: extract the ZIP and run SonicTheHedgehog2Recomp.exe. Keep assets/ beside it. Select your Sonic 2 (World) Rev A / REV01 ROM in the launcher and optional Amy/S3&K donor ROMs under Mods. No ROMs, settings, or saves are included.

Party and campaign saves remain local-only and cannot be combined with machine quickstates or netplay.

Source: https://github.com/mstan/SonicTheHedgehog2Recomp (tag v0.6.1). PolyForm Noncommercial 1.0.0; third-party notices are included.

Release check: downloaded the published Windows ZIP, verified it matches the uploaded package, extracted it into a clean directory, and reached Emerald Hill through the save menu with Knuckles, Sonic, Tails and Amy. Sonic 2/Amy/S3&K ROM paths were prefilled locally. The downloaded build was left running for the owner.

Sonic 2 v0.6.0 — Local party and campaign saves

Sonic 2 v0.6.0 adds optional local party play and Sonic 3-style campaign saves.

• Sonic 3-style Save Menu: enable it under Mods > S3&K after selecting your combined Sonic 3 & Knuckles ROM. Eight slots, No Save, animated Delete, zone/act names, Chaos Emeralds and completed-file zone selection. Off by default and independent of Knuckles.
• Campaign SRAM picker: lives under the save-menu mod. Load and update a chosen file anywhere, or let the first save create sonic2-campaign.srm beside the executable. Paths inside the game folder remain relative; existing .sav progress is preserved. Saves use validated external data and a backup; neither ROM is modified.
• Local party Options: up to four unique player/CPU character slots, with optional Amy and Knuckles using owner-supplied donor ROMs. Native Sonic/Tails special stages return to the chosen party. The save menu always shows Sonic & Tails; Options determines the actual roster.
• Existing optional adaptive widescreen remains available.

Windows x64: extract the ZIP and run SonicTheHedgehog2Recomp.exe. Keep assets/ beside it. Supply your Sonic 2 (World) Rev A / REV01 ROM; optional donors are selected under Mods. No ROMs, settings, or saves are included.

Party and campaign saves are local-only and cannot be combined with machine quickstates or netplay. Saves retain progress and Emeralds, with fresh lives on load. This release does not claim exhaustive whole-campaign or four-controller certification.

Source: https://github.com/mstan/SonicTheHedgehog2Recomp (tag v0.6.0). PolyForm Noncommercial 1.0.0; third-party notices are included.

Release check: downloaded the published Windows ZIP, extracted it into a clean directory, configured Sonic 2/Amy/S3&K ROM paths, and reached Emerald Hill through the save menu with Knuckles, Sonic, Tails and Amy. The first save created the external campaign SRAM file.

Sonic 2 v0.5.0 — Opt-in adaptive widescreen

Sonic 2 v0.5.0 — Opt-in adaptive widescreen

• Enable Widescreen under Mods: Adaptive, 16:9, 21:9, or 32:9. It is off by default.
• Custom stage/background rendering, expanded object spawning/culling and rings, and a screen-anchored gameplay HUD.
• Full-width title scenery, fades and transitions. Adaptive can extend beyond 32:9.
• Stable sprite publication prevents ring/HUD flicker. Opt-in CPU headroom avoids the original hardware budget slowing expanded gameplay; normal VBlank and sound clocks remain intact.
• Verified one gameplay update per VBlank on Emerald Hill, Metropolis and Casino Night routes, plus real-time Adaptive at 2676x374. Water, special-stage scenery, live resizing and native regression checks passed.

Experimental limits: the special-stage half-pipe remains centered; native two-player competition stays unchanged. Whole-stage views can exhaust the original object pool and require more host rendering time. This is not full-game/boss-route certification.

Windows x64: extract the zip and run SonicTheHedgehog2Recomp.exe. Keep assets/ beside it. Supply your own Sonic 2 (World) Rev A / REV01 ROM; none is included. Settings and saves are not bundled.

Source: https://github.com/mstan/SonicTheHedgehog2Recomp (tag v0.5.0). PolyForm Noncommercial 1.0.0; permissive third-party notices are included.

v0.4.0 — Pre-boot launcher UI

New: RmlUi pre-boot launcher UI. Launch Sonic 2 through a graphical front-end
that verifies your ROM, lets you configure controllers (keyboard + gamepad,
rebindable, 2-player, 3/6-button), and adjust settings (widescreen, intro skip,
window scale, volume) before the game boots.

Built on the AGPL-free clean-room own backend (own VDP/bus/Z80 scheduler, ymfm FM,
superzazu Z80). Ships under PolyForm Noncommercial 1.0.0 + permissive third-party
notices.

Windows (win64): download the zip, unzip, and run SonicTheHedgehog2Recomp.exe.
Bring your own Sonic 2 ROM (sonic2.bin) — none is included. The launcher/ assets
folder must stay next to the exe.

Built from engine 5c165f6 (segagenesisrecomp v0.1.0).

Sonic2 — Linux (AppImage, initial/experimental)

Initial experimental Linux release — x86_64 AppImage.

Bring your own ROM. Place your legally-dumped Sonic the Hedgehog 2 (.bin/.md/.gen) ROM in the same folder as the AppImage; it's auto-detected at launch. No ROM is included.

Run it

chmod +x Sonic2-x86_64.AppImage
./Sonic2-x86_64.AppImage          # add --appimage-extract-and-run if FUSE is unavailable

Steam Deck / controllers — the AppImage reads the controller natively. In Desktop mode, launch through Gaming Mode (or set a Gamepad controller layout) so face buttons aren't remapped to keyboard keys.

Production build — no debug server / tooling. Early, experimental Linux port; expect rough edges. Source: this repo.

Licensed under PolyForm Noncommercial 1.0.0 (LICENSE.md). Native AGPL-free build; third-party notices in THIRD-PARTY-LICENSES.md (both attached).

v0.3.0 — AGPL-free native build + audio delivery fixes

First release of the clean-room own backend: recompiled 68000, own VDP/bus/scheduler, ymfm FM (BSD-3), superzazu Z80 (MIT), clean-room SN76489. Zero AGPL code linked or compiled — ships under PolyForm Noncommercial 1.0.0 (see LICENSE and THIRD-PARTY-LICENSES.md in the zip).

Audio: SDL delivery servo with silence priming (eliminates queue underrun splices), interrupt-handler audio timestamp re-base, multi-frame event spreading for long PCM bursts.

Bring your own ROM: place sonic2.bin next to the exe. No game data is distributed.

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macOS (Apple Silicon) build — SonicTheHedgehog2Recomp-macos-arm64.zip

Native arm64 .app (SDL2 bundled, ad-hoc signed). ROM not included.