diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index dac480a..bf0980a 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -81,9 +81,12 @@ jobs:
         run: |
           sudo apt-get update && sudo apt-get install -y nsis p7zip-full
           VERSION="$(sed -n 's/.*config\/version="\([^"]*\)".*/\1/p' project.godot)"
-          makensis /DVERSION="$VERSION" \
-            /DARTIFACT="build/step-line-windows-$VERSION.exe" \
-            /DICON=packaging/windows/step-line.ico \
+          # NOTE: on Linux, makensis uses -D defines (the /D form is Windows-only
+          # and is rejected as a script path).
+          makensis \
+            -DVERSION="$VERSION" \
+            -DARTIFACT="build/step-line-windows-$VERSION.exe" \
+            -DICON=packaging/windows/step-line.ico \
             packaging/windows/step-line.nsi
 
       - name: Verify Windows installer contents
diff --git a/packaging/linux/build_appimage.sh b/packaging/linux/build_appimage.sh
index c079941..5d2f33a 100644
--- a/packaging/linux/build_appimage.sh
+++ b/packaging/linux/build_appimage.sh
@@ -27,8 +27,11 @@ cp "$HERE/step-line.desktop" "$APPDIR/step-line.desktop"
 cp "$HERE/AppRun" "$APPDIR/AppRun"
 chmod +x "$APPDIR/AppRun"
 cp "$HERE/step-line.png" "$APPDIR/step-line.png"
-mkdir -p "$APPDIR/usr/share/metainfo"
-cp "$HERE/step-line.appdata.xml" "$APPDIR/usr/share/metainfo/step-line.appdata.xml"
+# Desktop entry + metainfo in standard locations (AppStream validation requires
+# the metainfo filename to match the component id, and the .desktop discoverable).
+mkdir -p "$APPDIR/usr/share/applications" "$APPDIR/usr/share/metainfo"
+cp "$HERE/step-line.desktop" "$APPDIR/usr/share/applications/step-line.desktop"
+cp "$HERE/step-line.appdata.xml" "$APPDIR/usr/share/metainfo/net.stepline.game.appdata.xml"
 
 TOOL="${APPIMAGE_TOOL:-/tmp/appimagetool-x86_64.AppImage}"
 if [[ ! -f "$TOOL" ]]; then
diff --git a/packaging/linux/step-line.appdata.xml b/packaging/linux/step-line.appdata.xml
index d8d00d4..fae1183 100644
--- a/packaging/linux/step-line.appdata.xml
+++ b/packaging/linux/step-line.appdata.xml
@@ -1,8 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <component type="desktop-application">
-  <id>net.step-line.StepLine</id>
+  <id>net.stepline.game</id>
   <name>Step Line</name>
   <summary>Workplace security simulation on Hollywood Boulevard</summary>
+  <url type="homepage">https://git.allucanget.biz/zwitschi/security-game</url>
+  <developer id="net.stepline"><name>Step Line Team</name></developer>
   <description>
     <p>
       Step Line is a workplace security simulation about observation, communication,
diff --git a/squashfs-root/.DirIcon b/squashfs-root/.DirIcon
new file mode 120000
index 0000000..0e7fb9f
--- /dev/null
+++ b/squashfs-root/.DirIcon
@@ -0,0 +1 @@
+appimagetool.png
\ No newline at end of file
diff --git a/squashfs-root/AppRun b/squashfs-root/AppRun
new file mode 100755
index 0000000..4bc2d84
--- /dev/null
+++ b/squashfs-root/AppRun
@@ -0,0 +1,10 @@
+#! /bin/sh
+
+set -e
+
+this_dir="$(dirname -- "$(readlink -f -- "$0")")"
+
+# make appimagetool prefer the bundled mksquashfs
+export PATH="$this_dir"/usr/bin:"$PATH"
+
+exec "$this_dir"/usr/bin/appimagetool "$@"
diff --git a/squashfs-root/appimagetool.desktop b/squashfs-root/appimagetool.desktop
new file mode 120000
index 0000000..3a632fb
--- /dev/null
+++ b/squashfs-root/appimagetool.desktop
@@ -0,0 +1 @@
+usr/share/applications/appimagetool.desktop
\ No newline at end of file
diff --git a/squashfs-root/appimagetool.png b/squashfs-root/appimagetool.png
new file mode 120000
index 0000000..6fad5e6
--- /dev/null
+++ b/squashfs-root/appimagetool.png
@@ -0,0 +1 @@
+usr/share/icons/hicolor/128x128/apps/appimagetool.png
\ No newline at end of file
diff --git a/squashfs-root/usr/bin/appimagetool b/squashfs-root/usr/bin/appimagetool
new file mode 100755
index 0000000..2b81f74
Binary files /dev/null and b/squashfs-root/usr/bin/appimagetool differ
diff --git a/squashfs-root/usr/bin/desktop-file-validate b/squashfs-root/usr/bin/desktop-file-validate
new file mode 100755
index 0000000..3d8b3f5
Binary files /dev/null and b/squashfs-root/usr/bin/desktop-file-validate differ
diff --git a/squashfs-root/usr/bin/mksquashfs b/squashfs-root/usr/bin/mksquashfs
new file mode 100755
index 0000000..299f3ab
Binary files /dev/null and b/squashfs-root/usr/bin/mksquashfs differ
diff --git a/squashfs-root/usr/bin/zsyncmake b/squashfs-root/usr/bin/zsyncmake
new file mode 100755
index 0000000..5dae565
Binary files /dev/null and b/squashfs-root/usr/bin/zsyncmake differ
diff --git a/squashfs-root/usr/share/applications/appimagetool.desktop b/squashfs-root/usr/share/applications/appimagetool.desktop
new file mode 100644
index 0000000..86eabaf
--- /dev/null
+++ b/squashfs-root/usr/share/applications/appimagetool.desktop
@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Application
+Name=appimagetool
+Exec=appimagetool
+Comment=Tool to generate AppImages from AppDirs
+Icon=appimagetool
+Categories=Development;
+Terminal=true
+
diff --git a/squashfs-root/usr/share/icons/hicolor/128x128/apps/appimagetool.png b/squashfs-root/usr/share/icons/hicolor/128x128/apps/appimagetool.png
new file mode 100644
index 0000000..a304efd
Binary files /dev/null and b/squashfs-root/usr/share/icons/hicolor/128x128/apps/appimagetool.png differ
diff --git a/squashfs-root/usr/share/metainfo/appimagetool.appdata.xml b/squashfs-root/usr/share/metainfo/appimagetool.appdata.xml
new file mode 100644
index 0000000..0f7da9c
--- /dev/null
+++ b/squashfs-root/usr/share/metainfo/appimagetool.appdata.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop">
+  <id>appimagetool.desktop</id>
+  <metadata_license>MIT</metadata_license>
+  <project_license>MIT</project_license>
+  <name>appimagetool</name>
+  <summary>Create AppImage files</summary>
+  <description>
+    <p>
+      appimagetool is a tool that lets you generate AppImage files. An AppImage
+      is a self-running bundle that contains an application and everything
+      it needs to run that cannot reasonably expected to be part of each target system.
+    </p>
+    <p>
+      This can include libraries that are not commonly available on target systems,
+      resources such as translations, icons, fonts, and other auxiliary files.
+      appimagetool makes it easy to take an AppDir (e.g., generated by linuxdeployqt)
+      and turn it into an AppImage.
+    </p>
+    <p>
+      You can also embed update information so that your users can update the AppImage
+      using binary delta updates with the AppImageUpdate tool.
+      You can also sign the AppImage with GPG.
+    </p>
+  </description>
+  <url type="homepage">https://github.com/AppImage/AppImageKit</url>
+  <project_group>AppImage</project_group>
+  <provides>
+    <binary>appimagetool</binary>
+  </provides>
+</component>