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

[!IMPORTANT]
You need your own copy of the original screensaver files. This project does not include them
(see What you need).

Get started

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.

Your system refuses to open the file?

The program is not code-signed, so your system may warn about it.

• Windows: in the SmartScreen window, click More info, then Run anyway.
• macOS: open Terminal in the folder and run
  chmod +x open-scrantic-macos && xattr -d com.apple.quarantine open-scrantic-macos, then
  ./open-scrantic-macos.
• Linux: run chmod +x open-scrantic-linux-x64, then ./open-scrantic-linux-x64. If it complains
  about a missing sound library, install ALSA (libasound2 on Debian and Ubuntu).

What you need

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

File	Size	What it is
SCRANTIC.SCR	295,952	the original screensaver program
RESOURCE.MAP	1,461	index of the screensaver's resources
RESOURCE.001	1,175,645	the images and animation scripts

Check that your files are the right ones

File	SHA-256
SCRANTIC.SCR	7811b526b36bba2f08326d7a680f2f063190b4278e5a36393fde5a02080b0262
RESOURCE.MAP	3d9ec330aab96bbe5a44ce34f5945703862e82b195088590b7adfef5d7345da7
RESOURCE.001	df9c2213f7c0abacf4e302cb53a476f9f220579c07ba350b167e351eed548eae

Run shasum -a 256 SCRANTIC.SCR RESOURCE.MAP RESOURCE.001 (macOS) or sha256sum (Linux) and compare.
On Windows, use certutil -hashfile <file> SHA256.

Settings

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):

Key	Effect when off
Background	no island or ocean background
Clouds	no clouds in the sky
Waves	no shore waves or ocean whitecaps
Sounds	sound effects muted

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

Story state (advanced)

Maintained by the program; edit only to force a chapter or time of day.

Key	Default	Meaning
NumDays	0	story chapter of the day, 1–11; advances once per calendar day
Introduction	0	next chapter to show; the chapter plays when it is <= NumDays
CurrentYear, CurrentMonth, CurrentDay	0	date of the last run, used to detect a new day
StartTime	900	start of the 16-half-hour day/night cycle, as HHMM

An out-of-range NumDays (below 2 or above 11) restarts the story at chapter 1 on the next day
change.

FAQ

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).

Why this exists

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.

About the project

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.

For developers

Build from source

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.

Option	Effect
--fullscreen	start fullscreen instead of windowed
--dedither	blend the 1992 checkerboard dithering into solid colors
--soft-audio	improve the sounds: resample, hide the 8-bit hiss, fade cuts
-V, --version	print the version and exit
-h, --help	print the usage and exit

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

Development

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.

Contributing

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.

Releases

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.

AI disclosure

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.

Legal notice

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.

License

Source code under the MIT License.