glauberlima/open-scrantic

🏝️ Open Scrantic

Johnny Castaway, the classic 1992 screensaver, running natively on Windows, macOS and Linux.

▶ Watch a 30-second demo

Open Scrantic brings the original Screen Antics: Johnny Castaway screensaver (Sierra/Dynamix, 1992) back to modern computers: a free, open-source Rust reimplementation of the classic Windows 3.1 screensaver. Watch Johnny go about his days on his tiny island while a story unfolds from one day to the next, with the same behavior as the original.

Get started · Settings · FAQ · Why · For developers · AI disclosure · Legal

1. Download the program for your system from the latest release:

   System	File
   Windows	open-scrantic-windows-x64.exe
   macOS	open-scrantic-macos
   Linux	open-scrantic-linux-x64

2. Put it in the same folder as the three original screensaver files (SCRANTIC.SCR, RESOURCE.MAP and RESOURCE.001).

3. Run it. It opens in a window; press Esc to exit. Start it with --fullscreen to fill the screen. F12 saves a screenshot (-raw as drawn, -view as shown) next to the executable.

The three files from the original Screen Antics: Johnny Castaway installation (Windows 3.1), all in one folder next to the program:

Options and story progress are stored in SCRANTIC.INI, next to the program. It is created on the first run and rewritten when you exit normally, so edit it only while the program is closed. Keys are case-insensitive.

Options (0 = off, 1 = on; default 1):

To start over, delete SCRANTIC.INI. If it contains an invalid value, it is replaced by the defaults, story progress included.

Why do I need the original files? The art, animation scripts and sounds are copyrighted by their owners. This project reimplements only the engine and reads those assets when it runs.

Does it work with any build of the screensaver? No. The loader checks known strings in SCRANTIC.SCR and rejects other builds of the executable.

Where is my progress saved? In SCRANTIC.INI (see Settings).

Because it's cool, and because it's nostalgic. Johnny Castaway takes me back to my childhood, to simpler times, and I wanted it to keep running on the computers we use today, for me and for anyone else who remembers it.

Open Scrantic is a reverse-engineered reimplementation of Screen Antics: Johnny Castaway (Sierra/Dynamix, 1992), rebuilt from the disassembly of the original Windows 3.1 screensaver. The program contains only the engine logic.

SCRANTIC.SCR ──► assets::exe       ──► sounds, scene catalog, walk routes, RNG seed
RESOURCE.MAP ─┐
RESOURCE.001 ─┴► assets::resource  ──► images, palette, TTM/ADS scripts
                                              │
                    engine: story planner ──► ADS scheduler ──► TTM frames ──► canvas
                    (calendar, chapters)      (z-order, tags)   (draw, sound)    │
                                                                      winit + softbuffer + rodio

The disassembly is the ground truth for behavior, including the original 16-bit arithmetic and random number generator. Recovered formats, VM semantics, story rules, timing and the deliberate deviations (for example, full-frame redraw instead of dirty rectangles) are recorded in docs/ENGINE.md. The original settings dialog is not reimplemented; options live in SCRANTIC.INI.

Requires Rust 1.99.1 (pinned in rust-toolchain.toml). On Linux, also install the ALSA headers and pkg-config (libasound2-dev pkg-config on Debian and Ubuntu).

cargo build --release
cp /path/to/install/{SCRANTIC.SCR,RESOURCE.MAP,RESOURCE.001} target/release/
target/release/open-scrantic

The screensaver files and SCRANTIC.INI are always read from the directory of the executable.

The release profile is optimized and portable (fat LTO, a single codegen unit, panic = "abort", stripped symbols). For a binary tuned to the build machine only (it may not run on older CPUs):

RUSTFLAGS="-C target-cpu=native" cargo build --release

OPEN_SCRANTIC_DEBUG=1 target/release/open-scrantic              # prints each session's plan
cargo run --release --example snapshot -- /path/to/install /tmp/out 2000 100 1000 42   # headless PNG render

Architecture (the full write-up, with the data flow and how a frame is produced, is in docs/ARCHITECTURE.md):

• src/assets/ — reading the original files: the Dynamix resource archive (RLE/LZW, BMP, SCR, PAL, TTM, ADS) and the NE executable (WAVESFXn sounds and data-segment tables).
• src/engine/ — the engine: TTM VM (ttm.rs), ADS VM and scene scheduler (ads.rs), island and ambient animation (island.rs), walking (walk.rs), story planning (mod.rs), the original random number generator (rng.rs), drawing primitives (gfx.rs), INI settings (config.rs).
• src/main.rs — window (winit + softbuffer), clocks and input; src/present.rs — frame to window pixels (dedithering, scaling); src/audio.rs — sound (rodio).

See AGENTS.md for the full architecture notes and conventions.

Run these before sending changes; warnings fail the build (Cargo.toml denies them):

cargo clippy --all-targets
cargo fmt --check
OPEN_SCRANTIC_DATA=/path/to/install cargo test

Commits follow Conventional Commits. Never commit screensaver data. When porting more logic, cite the original address in the comment (seg10:1acb, DS:1756), as existing code does.

CI (format, clippy, release build on Linux, macOS and Windows) runs on every pull request and push to main. A release is cut manually from the Release workflow (Actions tab): it derives the next version from the Conventional Commits since the last tag (git-cliff), builds the three binaries, scans them with VirusTotal, commits the updated CHANGELOG.md, tags the version and publishes the GitHub release with the binaries and their SHA-256 checksums. If no commit since the last tag deserves a release (feat, fix, perf, refactor, docs), nothing is published.

Generative AI was used throughout the development of Open Scrantic. The project was built with Claude Code (Anthropic) together with REA: Reverse Engineer Anything, a reverse-engineering toolkit exposed to the model. Together they were used to disassemble and decompile the original SCRANTIC.SCR, recover the resource formats and script semantics, and write the Rust code, tests and documentation. The developer directed the work and reviewed and integrated the AI-assisted results, checking the behavior against the original screensaver.

Screen Antics: Johnny Castaway is a trademark and copyright of its respective owners (Sierra / Dynamix). This is an independent, non-commercial interoperability project, not affiliated with or endorsed by them. It does not include or distribute any original screensaver data.

Source code under the MIT License.