OpenSE4 0.15.0

OpenSE4 is an open-source engine for Space Empires IV Deluxe. It plays the classic game on your own installed copy of Space Empires IV Deluxe and contains nothing from the original game.

OpenSE4 is not affiliated with, endorsed by or sponsored by the game's publishers.

What changed since 0.14.1

This release is an accuracy pass. While fixing a report earlier this week, we found that the tool we use to read the original game's code had been hiding part of many routines from us. About 400 routines had lost real game logic that way, and more were misread as returning early. We repaired the tool, then checked every area of OpenSE4 against the complete code of SE4 again: movement, orders, cargo and colonization; the economy and events; combat; the computer players; research, intelligence and diplomacy; the galaxy, setup and saved games; and the interface. About 150 differences were found and corrected. As before, OpenSE4's own additions stay, and where one changes what you see or how the game plays, it is now an option that starts off. See "New options" below.

Ship movement, exactly as in SE4

• The turn is invisible. As in SE4, a ship doesn't visibly rotate before it moves: it waits on its square for the time of the turn, then slides off already facing its new way. We checked this in the running original.
• One group at a time, as in SE4, now with the original's details:
  • your ships at the start of your turn are each selected, then moved;
  • a fleet is drawn as its first ship;
  • a minefield hit plays its explosion, sound and pause;
  • the move into a battle is shown before the battle.
• A turn's start stops at the Attack Sector question. Later groups move only after you answer.
• Input during moves follows the original:
  • after a map-click order, clicks and keys wait until the ships have moved;
  • after an order button, you can carry on.
  • A click or key at the start of your turn still skips the animation.
• The original's selection after a move: a move order leaves the top-left square of the system current, as in SE4.
• Computer players' moves are no longer animated, as in SE4. A new option brings that back (see below).
• Network games: your own ships now move square by square in network games too.

Rules corrected (selected)

• Orders and cargo:

  • Load Cargo takes only from your colonies and bases, never from other ships, and a plague doesn't stop it.
  • Tagged ships share one worked-out Explore or Colonize plan.
  • Set Patrol starts only when the route is closed.
  • Most failed orders say nothing, as in SE4; the new "Explain failed orders" option brings our messages back.

• Colonization: founding a colony gives the empire 100 experience. The colony ship unloads by the Drop Cargo rules, and a Medical Bay cures plague as it passes.

• Fleets: default fleet names count every fleet ever made. Empty fleets last until the game is loaded again.

• Economy and events:

  • a captured capital stays a capital;
  • a lost planet's happiness events come only when its people die out;
  • starting population leaves out the storage trait;
  • at most five timed events wait at once;
  • riots follow anger alone;
  • Team Mode ignores treaty happiness;
  • the Planetary minister's mood reports are new.

• Combat:

  • targets are picked with the original's sort and the original's strength, size and damage measures;
  • a missile's hit credits no experience;
  • launched units and battle minefields are real objects at once;
  • every ground unit rolls;
  • damage pools are capped.

• Computer players:

  • their fleets keep receiving orders after defending;
  • fleet roles and sizes follow the fleets in being;
  • attack, patrol and exploration follow the original's rules;
  • their construction list stops where SE4's does;
  • their demand lists are forgotten when a game is loaded.

  Their pace is now closer to the original's in exploration, infrastructure and ships.

• Diplomacy and intelligence:

  • a technology item in a trade gives one level;
  • only the newest message from an empire can be answered;
  • Break Treaty ends a war;
  • surrendered ships leave their fleets;
  • spying results and failures follow the original;
  • Select Package adds amounts in the original's steps.

• End of game:

  • once a game is decided, its last turn skips the economy and the computer players;
  • a simultaneous game goes on after a victory, as in SE4.

• Galaxy and setup:

  • Create Black Hole destroys planets outright;
  • every ship in a group with a stellar manipulation device acts;
  • Construct needs the exact size;
  • Quick Start builds your empire like a computer player's.

• Saved games:

  • experience in saves of the original from versions 1.40 to 1.45 is read correctly;
  • a save holding designs owned by no player imports.

• Command line: the original's command line behaves as in SE4: missing files, -nd, and signing in.

• Interface:

  • tags stay through the ship cycle until Shift+C or a sector click;
  • the ship, fleet and colony cycles continue where they left off;
  • the sector list shows a design's class only under your own ships;
  • Drop Cargo asks the cargo kind first;
  • held keys repeat;
  • the Component Report shows the original's lines.

The rules are written in docs/spec/, each corrected answer marked "corrected 2026-10-14, complete listing". What OpenSE4 still does differently on purpose is in docs/PARITY_GAPS.md.

New options (all off by default, under Options → OpenSE4)

• Also animate other empires' and simultaneous turns' moves
• Explain failed orders
• More in item reports
• Say on the map why a click fired nothing (tactical combat)
• Clear tags when selecting a ship elsewhere
• Show enemy designs' details
• Act once on held keys
• Game Setup's Save To File saves the designs

Compatibility

0.15.0 does not play with 0.14.x. Network and e-mail games need everyone on 0.15.0 (protocol 10). 0.15.0 loads saves from 0.14.x and older (save format 11 now), but 0.14.x cannot load 0.15.0's saves. Games continued from a save play by the corrected rules from then on, and the computer players play differently. Every player in a network game must have the same game-changing mods.

Downloads

File	For
OpenSE4-0.15.0-windows-x86_64-setup.exe	64-bit Windows 7 SP1 to 11: the installer
OpenSE4-0.15.0-windows-x86_64.zip	64-bit Windows 7 SP1 to 11: the same programs to run from any folder
OpenSE4-0.15.0-linux-x86_64.tar.gz	64-bit Linux on PCs with glibc 2.34 or later (Ubuntu 22.04, Debian 12, Fedora 35, SteamOS 3 and newer)
OpenSE4-0.15.0-linux-aarch64.tar.gz	64-bit ARM Linux with glibc 2.34 or later (Raspberry Pi OS 64-bit, Asahi, Ubuntu and Debian on ARM)
OpenSE4-0.15.0-linux-armhf.tar.gz	32-bit ARM Linux (ARMv7 with NEON) with glibc 2.34 or later (Raspberry Pi OS 32-bit)
OpenSE4-0.15.0-SHA256SUMS.txt	SHA-256 checksums of the downloads

Every download holds five programs:

• the game (opense4);
• the dedicated server for network and play-by-e-mail games (opense4-server);
• a data checker (opense4-datacheck);
• the saved-game converter (opense4-convert);
• the modding tool (opense4-sdk).

It also holds the Hegemon mod (mods/; turn it on in the Mods window), the modder's documents and examples (sdk/) and, in the zip and tarballs, PORTABLE-README.txt. Libraries, our own fonts, the manual and the lessons are built in.

Running it

• Windows: run the installer, then start OpenSE4 from the Start menu, or unpack the zip and run opense4.exe. Neither is code-signed yet, so Windows SmartScreen may warn the first time ("More info", then "Run anyway").
• Linux, on a PC or on ARM: unpack and run ./opense4, or run ./install-desktop-entry.sh once to start it from your desktop's application list. On ARM boards without a Steam install, copy the game's files from another computer (see docs/SETUP.md).

The game looks for a Steam install of Space Empires IV Deluxe. See README.md for other locations and command-line options (opense4 --help). Modders start with sdk/docs/README.md.

Known limitations

• This is still an early build, marked as a pre-release.

• Details still being checked: where the original's behaviour couldn't be pinned down, OpenSE4 makes a stated choice. These choices are listed as open questions in docs/spec/, for example how the original treats a mine group chosen in battle, or the default names past the tenth fleet.

• Original .map files: reading them has only been tested with maps OpenSE4 wrote, since no map file from the original was at hand. Reports with real map files are welcome.

• Not yet tested on real hardware:

  • Windows 7: only under Wine, with each program's imports checked against what Windows 7 provides.
  • ARM: only through emulation and native ARM test runners; the game window hasn't been opened on a real ARM graphics chip yet.

  Reports are welcome.

• Scripts run on MicroPython: in-game scripts use a built-in, sandboxed Python (MicroPython with additions), so libraries such as numpy are only available to external bots.

• Rules mods near their time limit: a rules mod that runs very close to its per-turn time limit could, rarely, replay a turn slightly differently.

• Hegemon rarely finishes off an empire within 150 turns; it wins by growing far ahead.

• Following warps: the view follows your ships through warp points in local, hotseat and e-mail games, but not yet for players who join someone else's network game.

• In network and e-mail games, every battle is resolved strategically, as in the original.

License

OpenSE4 is free software under the GNU General Public License, version 3 or later. The Noto Sans fonts are under the SIL Open Font License. THIRD_PARTY_NOTICES.txt in each download lists the bundled libraries and their licences, among them MicroPython and miniz.