diff --git a/common/pkgs/rars-flatlaf/default.nix b/common/pkgs/rars-flatlaf/default.nix
new file mode 100644
index 0000000..d438046
--- /dev/null
+++ b/common/pkgs/rars-flatlaf/default.nix
@@ -0,0 +1,100 @@
+{
+  stdenvNoCC,
+  jre,
+  fetchFromGitHub,
+  fetchurl,
+  makeWrapper,
+  makeDesktopItem,
+  rsync,
+  ...
+}:
+stdenvNoCC.mkDerivation rec {
+  name = "rars-flatlaf";
+
+  src = fetchFromGitHub {
+    owner = "privat";
+    repo = "rars";
+    rev = "fd34014efd65b3cb5a52f1729c3b8240cae0c332";
+    hash = "sha256-D8X/cr+fnq/OOFYfMG9aPss95J8Z2yiROuF9kmHkK40=";
+    fetchSubmodules = true;
+  };
+
+  desktopItem = makeDesktopItem {
+    name = "RARS";
+    desktopName = "RARS";
+    exec = name;
+    icon = name;
+  };
+
+  nativeBuildInputs = [makeWrapper rsync jre];
+
+  installPhase = let
+    flatlaf = fetchurl {
+      url = "https://repo1.maven.org/maven2/com/formdev/flatlaf/3.2/flatlaf-3.2.jar";
+      hash = "sha256-HAG+G9undDXWtySokKl7lkIUCFI7lEBduu+UgSVaxAA=";
+    };
+    icon = fetchurl {
+      url = "https://riscv.or.jp/wp-content/uploads/2019/06/cropped-RISC-V-logo-figonly-mod-2.png";
+      hash = "sha256-e1/iVmadVzyO77ikBr1cdXsJdDj8TiXh3Oyjek9GwqM=";
+    };
+  in
+    /*
+    bash
+    */
+    ''
+      # ./build-jar.sh
+      mkdir -p build
+      find src -name "*.java" | xargs javac --release 8 -d build
+      if [[ "$OSTYPE" == "darwin"* ]]; then
+          find src -type f -not -name "*.java" -exec rsync -R {} build \;
+      else
+          find src -type f -not -name "*.java" -exec cp --parents {} build \;
+      fi
+      cp -rf build/src/* build
+      rm -r build/src
+      cp README.md License.txt build
+      cd build
+      jar cfm ../rars.jar ./META-INF/MANIFEST.MF *
+      chmod +x ../rars.jar
+
+      cd ..
+
+      # ./build-jar-flatlaf.sh
+      mkdir -p build-flatlaf/
+      cd build-flatlaf/
+
+      cp ${flatlaf} ../flatlaf.jar
+
+      jar x < ../rars.jar
+      jar x < "../flatlaf.jar"
+
+      cat > META-INF/MANIFEST.MF <<EOF
+      Manifest-Version: 1.0
+      Implementation-Version: 3.1.1
+      Multi-Release: true
+      Main-Class: rars.Launch
+      EOF
+
+      jar cfm ../rars-flatlaf.jar META-INF/MANIFEST.MF *
+      chmod +x ../rars-flatlaf.jar
+
+      cd ..
+
+      # InstallPhase
+      runHook preInstall
+
+      cat > ./rars.desktop <<EOF
+      EOF
+
+      mkdir -p "$out/share/pixmaps"
+      cp "${icon}" "$out/share/pixmaps/${name}.png"
+      install -D $desktopItem/share/applications/* $out/share/applications/rars.desktop
+
+      export JAR=$out/share/java/${name}/${name}.jar
+      install -D ./${name}.jar $JAR
+      makeWrapper ${jre}/bin/java $out/bin/${name} \
+        --add-flags "-jar $JAR"
+
+      runHook postInstall
+    '';
+}
diff --git a/modules/hyprland/default.nix b/modules/hyprland/default.nix
index dd72297..8c1c6ac 100644
--- a/modules/hyprland/default.nix
+++ b/modules/hyprland/default.nix
@@ -221,6 +221,7 @@ in {
       libreoffice-fresh # TODO: declarative conf?
       hunspell
       hunspellDicts.en_CA
+      config.customPkgs.rars-flatlaf
 
       # Apps
       thunderbird # TODO: use programs.thunderbird