Vendor the Shockolate engine and build it via a Docker image with every

dependency (SDL2, SDL2_mixer, fluidsynth-lite, a MIDI soundfont)
prebuilt, so compiling the engine needs no network access - just the
image and the engine source. Add res/assets/extract_assets.sh to pull
the game's data files out of a purchased GOG installer, and a Makefile
that assembles a runnable dist/ from the two.

Also add `make package`, which builds a redistributable tarball that
omits the proprietary game assets (shipping res/GET_ASSETS.txt instead)
plus license information for both the MIT tooling and the GPLv3 engine,
and a Gitea Actions workflow that builds and publishes it to
dl.ladkau.de on every push.

res/assets/GET_ASSETS.txt

@@ -0,0 +1,16 @@
+This package does not include System Shock's game data - it's
+copyrighted, proprietary content that can't be redistributed. To play,
+you need a copy of System Shock: Enhanced Edition (e.g. from gog.com).
+
+From your Enhanced Edition install, you need its classic-game data and
+sound files - the res/pc/hd/data and res/pc/cdrom/data trees merged
+together (res/pc/hd's copies win the couple of filenames present in
+both: intro.res, objprop.dat), and the res/pc/hd/sound tree, packed
+inside the install's sshock.kpf (a zip file).
+
+Copy that merged data into place, alongside this file:
+  res/data/   <- res/pc/hd/data + res/pc/cdrom/data, merged
+  res/sound/  <- res/pc/hd/sound
+
+Once res/data/ and res/sound/ exist next to this file, run ./run.sh from
+the root of this package to play.

res/assets/extract_assets.sh

@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+# Extracts the game data Shockolate needs out of a purchased System Shock:
+# Enhanced Edition installer from gog.com, into ./ss_ee/{data,sound}.
+#
+# Usage:
+#   1. Buy System Shock: Enhanced Edition on gog.com and download the
+#      offline installer (a Windows .exe, e.g.
+#      setup_system_shock_enhanced_edition_1.2.16_(64bit)_(44378).exe).
+#   2. Drop it in this directory (res/assets/).
+#   3. Run this script: ./extract_assets.sh
+#
+# The installer is an Inno Setup package; the actual game data lives
+# inside it in sshock.kpf, which is just a zip file. Its res/pc/hd/ and
+# res/pc/cdrom/ trees together hold every classic-game data/sound file
+# Shockolate's res/ folder expects (res/pc/hd wins the couple of
+# filenames present in both: intro.res, objprop.dat). Needs innoextract
+# and unzip; if they're not installed locally, this script does the
+# extraction inside a throwaway Ubuntu container instead (needs docker in
+# that case, nothing else).
+set -euo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")"
+ASSETS_DIR="$(pwd)"
+OUT_DIR="$ASSETS_DIR/ss_ee"
+
+fail() { echo "PREFLIGHT FAIL: $*" >&2; exit 1; }
+
+shopt -s nullglob
+installers=(setup_system_shock_enhanced_edition*.exe)
+shopt -u nullglob
+case "${#installers[@]}" in
+    0) fail "no setup_system_shock_enhanced_edition*.exe found in $ASSETS_DIR - buy System Shock: Enhanced Edition on gog.com, download the offline installer, and drop it here" ;;
+    1) ;;
+    *) fail "multiple installer .exe files found in $ASSETS_DIR - keep only one: ${installers[*]}" ;;
+esac
+INSTALLER="${installers[0]}"
+
+# Extracts sshock.kpf from $1 (an installer .exe) and assembles $2 (an
+# ss_ee output directory) from its res/pc/{hd,cdrom} trees. Defined as a
+# function so the exact same logic can run either natively or, via
+# `declare -f`, inside a throwaway container.
+run_extraction() {
+    set -euo pipefail
+    local installer="$1" out_dir="$2"
+    # Deliberately not `local`: an EXIT trap set here fires when the whole
+    # shell process exits, which is after this function - and this
+    # function's own scope - has already returned, so a `local` var would
+    # already be unset by then (unbound-variable error under `set -u`).
+    work="$(mktemp -d)"
+    trap 'rm -rf "${work:-}"' EXIT
+
+    echo "== Extracting sshock.kpf from installer =="
+    innoextract --silent --include sshock.kpf -d "$work/installer" "$installer"
+
+    echo "== Unpacking sshock.kpf (data/sound trees only) =="
+    mkdir -p "$work/kpf"
+    unzip -q "$work/installer/sshock.kpf" \
+        'res/pc/hd/data/*' 'res/pc/hd/sound/*' 'res/pc/cdrom/data/*' \
+        -d "$work/kpf"
+
+    echo "== Assembling $out_dir =="
+    rm -rf "$out_dir"
+    mkdir -p "$out_dir/data" "$out_dir/sound"
+    # cdrom/data first (cutscenes, audio logs, and shared tables only it
+    # has), then hd/data on top (wins the 2 overlapping filenames:
+    # intro.res, objprop.dat - the hd install's own copies).
+    cp -a "$work/kpf/res/pc/cdrom/data/." "$out_dir/data/"
+    cp -a "$work/kpf/res/pc/hd/data/." "$out_dir/data/"
+    cp -a "$work/kpf/res/pc/hd/sound/." "$out_dir/sound/"
+}
+
+if command -v innoextract >/dev/null 2>&1 && command -v unzip >/dev/null 2>&1; then
+    echo "== Using local innoextract/unzip =="
+    run_extraction "$ASSETS_DIR/$INSTALLER" "$OUT_DIR"
+else
+    echo "== innoextract/unzip not found locally - using a throwaway docker container =="
+    command -v docker >/dev/null 2>&1 \
+        || fail "docker not found in PATH (needed since innoextract/unzip aren't installed locally)"
+    docker run --rm \
+        -v "$ASSETS_DIR:/assets" \
+        -e HOST_UID="$(id -u)" \
+        -e HOST_GID="$(id -g)" \
+        ubuntu:22.04 \
+        bash -c "
+            set -euo pipefail
+            apt-get update -qq >/dev/null
+            apt-get install -y -qq innoextract unzip >/dev/null
+            $(declare -f run_extraction)
+            run_extraction '/assets/$INSTALLER' '/assets/ss_ee'
+            chown -R \"\$HOST_UID:\$HOST_GID\" /assets/ss_ee
+        "
+fi
+
+echo "== Done =="
+echo "Assets extracted to $OUT_DIR"
+echo "Note: mfdfrn.res/mfdger.res (French/German MFD art) are not present in this"
+echo "installer and are only needed for those localizations - not for English play."

res/run.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+# Launches System Shock. Copied next to the systemshock binary in dist/
+# by the root Makefile.
+set -euo pipefail
+cd "$(dirname "${BASH_SOURCE[0]}")"
+export LD_LIBRARY_PATH="$(pwd)/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
+exec ./systemshock "$@"