Strike Gunner S.T.G Recomp

A native recompilation of Strike Gunner S.T.G (USA), built on snesrecomp.

A vertical shoot-'em-up from 1992, recompiled from the 65816 to native code: the game's own logic runs as compiled C against an emulated SNES video chip, sound chip and DMA, with the framework's interpreter as a fallback for code no analysis has reached.

You must legally own a copy of the game. No ROM data is distributed with this project, in the repository or in any release. The recompiled C is generated locally from your own copy and is never committed.

Just want to play? Download the latest release from the Releases page and see PLAYING.md: setup, controls, options and how to report a problem. The rest of this file is for building and developing the port.

Mods

Optional extras on the launcher's Mods page, all off by default, so the game plays as the original unless you turn something on. Mix and match them freely.

Gameplay

• Stage select (new in 0.3.0): after you choose your special weapon, a list of the eight stages appears and the game goes to the one you pick. Show it before every stage or only when a game starts.
• One-hit kills (new in 0.3.0): every enemy, bosses included, goes down to the first hit. An easy mode, or a quick way through the game.
• Infinite special weapon (new in 0.3.0): the special weapon gauge never runs down, for either player.
• Infinite lives: losing a life never uses up a spare one, for both players.
• All weapons every stage: no weapon is ever marked NO USE on the weapon select screen.

Music

• Custom music (0.2.0): replace the game's music with your own. Drop WAV, MP3, OGG, FLAC or MSU-1 tracks into a folder per stage or screen (title, weapon select, each stage, boss, stage clear, game over, ending) and they play in their place, in order or at random, matched to the game's loudness. Seamless intro + loop pairs, short fades between songs, a small "now playing" caption with its own on/off switch, a skip key, and save states and rewind that resume the same song where it was. Sound effects are untouched.

How to set them up is in PLAYING.md.

Screenshots

Weapon select: 15 weapons to choose from	Stage 2: a bomber squadron
Stage 4: the fleet at sea	Stage 4: attacking a warship
Stage 6: the mothership in the asteroid field	Two players at once (2P START)

Status

Playable from start to finish (as of 2026-10-14): intro, attract demo, all stages, and the ending through the credits to "The End", in single-player play on Windows. Two-player play starts and both ships answer their own controller (headless check), and the launcher's second seat works with either player on keyboard or pad; a full 2P playthrough has not been done.

• Accuracy. Checked against snes9x with identical scripted input: game events land on the same frames for the first 3,162 frames of a 13,500-frame route, in both compiled and interpreted execution, and stage 4's heaviest section slows down exactly as much as on the reference (3,536 of 3,600 frames on time).
• Graphics. Correct throughout play, including save states loaded while paused.
• Audio. Matches the reference. The remaining occasional pops are in the game's own sound (see Options).
• Native code. 982 compiled variants, seeded from coverage captures of the intro, attract demo, stage 1, one full playthrough and the ending (recomp/coverage/). Uncovered code runs on the interpreter.
• Save states keep the frame driver's resume point, so a state resumes exactly where it was made (checked by saving, playing on, and reloading: identical memory and picture).
• Rewind (0.1.1): quarter-second steps, 25 seconds back by default, adjustable in the launcher. Committing a rewind lands exactly on the earlier frame (2 seconds back matched a plain run 120 frames earlier: memory, video memory, registers and picture), and committing, cancelling and opening work from keyboard and controller (checked by hand). Opening the save-state browser or rewind panel without committing leaves the game bit-identical.
• Setup packs. scripts/package_release.sh builds a setup pack that generates and builds the game on the player's PC from their ROM, with no Rust or other tools beyond what the launcher downloads. Checked on Windows from a fresh unzip: the code it generates matches a developer regeneration, and the game played through stage 1. Current release: 0.3.0 (tag v0.3.0). The framework's documentation and test suites are left out of packs.
• Mods: features on the launcher's Mods page, all off by default (mods/preloaded/packages/strikegunnerstg.gameplay). Off, the game is unchanged (attract run identical to the stock build).
  • Infinite lives (0.1.2, src/mod_infinite_lives.c): neither player loses spare lives.
  • All weapons every stage (0.1.3, src/mod_all_weapons.c): the used-weapon flags ($1BED / $1BFC, one byte per weapon) are cleared every frame, so the weapon select screen never marks a weapon NO USE.
  • One-hit kills (0.3.0, src/mod_one_hit_kill.c): the two damage tables in ROM ($00:E599 main gun by shot power, low byte; $00:E579 special weapons) are raised in memory (restored when off). Enemy health is offset 6 of the object slot, 200 at most. Large background-drawn enemies mirror their health into $1ADE (400 for the stage 4 warships); a drop of exactly the patched $FF there is finished, along with the enemy's own copy.
  • Infinite special weapon (0.3.0, src/mod_infinite_special.c): the gauges, 16-bit $023E / $0248 (full $0300), are put back when they drop.
  • Stage select (0.3.0, src/mod_stage_select.c): when the weapon is confirmed on the weapon select screen ($023D / $0247 set while its timer $0547 runs, not in the demo, $17E6), the framework's choice list opens and the pick goes into $0230, which the game reads after the screen ($00:8088). Leaving stage 1 replays the game's new-game resets ($00:808D-80B9).
  • Custom music (0.2.0, src/mod_custom_music.c): song commands on APU port 0 ($2140; $04 title, $03 weapon select, $01/$07/$06/$08/$09 stages, $02 boss, $0A stage clear, $05 game over, $01 in stage 8 the ending, $14 stop) are mapped to folders per stage and screen. A replaced song is swallowed, the driver is sent stop, and the player's track streams through the framework mixer, scaled to -21 dBFS RMS by default. Tracks load on a worker thread: WAV (smpl loops), MSU-1 .pcm, and MP3, OGG, FLAC through the public-domain decoders in third_party/audio/; an .intro./.loop. pair loops from the seam. Changes fade over 0.35 s. The song playing and its position are a tagged record ('STGN') after the STG1 save-state chunk, so loading a state or rewinding resumes it; a "now playing" caption uses the framework's bottom-anchored OSD caption (small proportional font, wraps onto a second line). The power-on driver upload on the same port is skipped. STG_MUSIC_LOG=<file> logs every decision.

Open items and what has been ruled out are in KNOWN_ISSUES.md.

ROM identity

File	Strike Gunner S.T.G (USA).sfc
Publisher	VAP (US licensee NTVIC)
Developer	Athena
Year	1992
Mapping	lorom
Region	USA (North America)
Coprocessor	none
CRC32	d054e288
SHA-256	05f14e6ed3394d9273e2397769a8acf1a9db646be6066e82269521e8eec53562

tools/regen.sh refuses to run against anything else, so a mismatched revision fails immediately instead of producing subtly wrong output.

Build

On Windows, configure with Ninja and clang (the retcomm cmake-clang-v1 toolchain): the default Visual Studio generator uses MSVC, which cannot compile the framework. The analyzer needs Rust (cargo) the first time.

git submodule update --init --recursive
bash tools/regen.sh --rom "/path/to/Strike Gunner S.T.G (USA).sfc"
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
cmake --build build -j

The snesrecomp submodule comes from a fork, SlippyGetBackHere/snesrecomp, branch local/mode2-renderer-fix: upstream plus sixteen changes this port needs that are not upstream. git clone --recursive fetches it. patches/README.md lists the fixes and how to re-apply them to upstream.

The ROM does not have to live in the repository — keeping it on your own drive is the better habit, and SNESRECOMP_ROM sets the path once for a shell. Without either, tools/regen.sh finds Strike Gunner S.T.G (USA).sfc at the repo root, then the path the setup wizard recorded in rom.cfg; .gitignore blocks both from ever being committed.

tools/regen.sh verifies the ROM, generates src/gen/*.c, and re-syncs recomp/funcs.h. Re-run it whenever you change anything under recomp/.

Run

./build/StrikeGunnerSTGSNESRecomp                     # launcher picks the ROM
./build/StrikeGunnerSTGSNESRecomp "/path/to/Strike Gunner S.T.G (USA).sfc" # or name it and skip the launcher

With no ROM on the command line the build opens the recomp-ui launcher: a ROM picker with a verification badge, plus display / audio / input settings. Your choice is cached in rom.cfg beside the executable, so the next launch opens on it and "Skip launcher on boot" makes it immediate. If the launcher is not built in (--no-recomp-ui), the host falls back to a native file picker.

Either way the ROM is checked against the digests above before anything boots — a dump that could not have produced this build is refused at the door rather than mis-executing ten frames in.

Options

strikegunner.ini beside the executable (created on first launch):

Key	Values
ReduceSlowdown	0 authentic console speed (default); 1, 2, 3 run the SNES CPU 2x, 3x, 4x faster
AudioDeclick	1 (default) caps sound samples that overflow instead of wrapping them, removing the loudest pops; 0 is the console's exact output

The game slows down where its logic needs more than a frame; at 1 the heaviest scene measured (stage 4, ocean section, extra fighters out) holds 60 fps. Frames that already fit are unchanged, so game speed and music stay authentic. Restart to apply. Some pops remain with AudioDeclick on: they are in the original game's sound (snes9x and footage of the console have them too). It is a separate file because the host rewrites config.ini from the settings it knows.

Layout

Path	What lives there
recomp/	Analysis input: bank*.cfg, symbols.toml, generated funcs.h
recomp/coverage/	Coverage captures that seed the analyzer (addresses and hit counts, no ROM data)
rom_identity.txt	ROM digests — read by the build, tools/regen.sh and CI
src/	Host code: main.c, game_rtl.c (frame driver, save-state hooks, options), gen_stubs.c (frame-wait and task-switch hand-backs)
src/gen/	Generated C. Never committed — regenerate locally
snesrecomp/	Framework submodule (owns lib/recomp-net, lib/retcomm-rbengine)
tools/	regen.sh — the ROM → C pipeline
scripts/	package_release.sh — player-facing zip
patches/	The local framework fixes, one patch per commit, with notes
framework_pins.txt	Exact framework commits this project is pinned to
KNOWN_ISSUES.md	Open issues, resolved ones, and what was ruled out

How the port works

• Frame driver (src/game_rtl.c). The framework's beam-aligned driver with one change: NMI is taken the way the CPU takes it, so the game's NMI handler -- which switches NMI off and runs for several frames during scene changes -- can span fields.
• Frame waits and task switches (recomp/bank00.cfg, bank05.cfg, src/gen_stubs.c). Compiled code cannot wait for the next frame, so the game's four wait routines and its cooperative task scheduler ($8D2E / $8D68) are declared hle_func and handed back to the driver's interpreter, which runs the original bytes.
• Object handlers (recomp/symbols.toml, bank03.cfg). All 165 entries of the object table at $03:8000 and the object loop are compiled, so enemies from every stage are native code.

Continuing

• Coverage. Play with --coverage-capture=on, add the capture from %LOCALAPPDATA%\snesrecomp-coverage\strikegunnerstg\ to recomp/coverage/, re-run tools/regen.sh, rebuild, and check the result plays the same. A new frame wait reached only from compiled code shows up as a hitch or freeze with an [interp_cap] line in the log; declare it like the others.
• Diagnostics. STG_AUDIOLOG=<file> logs the audio pipeline once a second. The framework's tools/snesref with a libretro SNES core is the reference for timing and audio comparisons.
• Never edit src/gen/ or synthesise a result to get past uncovered code. Fix the config or the framework and regenerate.

Multiplayer

Two players at once on one PC: 2P START on the title screen, one controller each (or rebind [player2] in keybinds.ini). Netplay is not built into this target.

License

This project's own source is under the license in LICENSE. The framework carries its own terms — see snesrecomp/LICENSE and snesrecomp/THIRD_PARTY_ATTRIBUTION.md. The audio decoders in third_party/audio/ are public domain (or MIT / MIT-0, your choice); see third_party/audio/README.md. None of these covers the game data, which is not distributed here.