diff --git a/build.sh b/build.sh
deleted file mode 100644
index 7c49d3d..0000000
--- a/build.sh
+++ /dev/null
@@ -1,17 +0,0 @@
-javac -classpath ~/Android/Sdk/platforms/android-34/android.jar java/classes/com/example/shadowing/MainActivity.java -d build/
-d8 --classpath ~/Android/Sdk/platforms/android-34/android.jar build/com/example/shadowing/MainActivity.class --output build/
-mkdir -p build/apk_files/
-cp build/classes.dex build/apk_files/
-~/Android/Sdk/build-tools/34.0.0/aapt package -v -f -M AndroidManifest.xml -I ~/Android/Sdk/platforms/android-34/android.jar -F build/app.apk build/apk_files/
-# Not working
-#~/Android/Sdk/build-tools/34.0.0/aapt2 link -v --manifest AndroidManifest.xml -I ~/Android/Sdk/platforms/android-34/android.jar -o build/app.apk build/apk_files/*
-if [ ! -f build/ToyKey.keystore ]; then
-  keytool -genkeypair -validity 1000 -dname "CN=SomeKey,O=SomeOne,C=FR" -keystore build/ToyKey.keystore -storepass 'P@ssw0rd!' -keypass 'P@ssw0rd!' -alias SignKey -keyalg RSA -v
-fi
-~/Android/Sdk/build-tools/34.0.0/zipalign -f 4 build/app.apk build/app.aligned.apk
-~/Android/Sdk/build-tools/34.0.0/apksigner sign -ks build/ToyKey.keystore --v2-signing-enabled true --in build/app.aligned.apk --out build/app.signed.apk --ks-pass 'pass:P@ssw0rd!'
-
-#~/Android/Sdk/platform-tools/adb install app.signed.apk
-#~/Android/Sdk/platform-tools/adb shell am start -n com.example.shadowing/.MainActivity
-#adb logcat -s SHADOWING
-#~/Android/Sdk/platform-tools/adb uninstall com.example.shadowing
diff --git a/flake.nix b/flake.nix
index 957956e..40b7726 100644
--- a/flake.nix
+++ b/flake.nix
@@ -57,6 +57,45 @@
           cat AndroidManifest.xml | sed 's/PACKAGE/${package}/' | sed 's/NAME/${name}/' > $out/AndroidManifest.xml
         '';
       };
+      keypass = "P@ssw0rd!";
+      keystore = pkgs.stdenvNoCC.mkDerivation {
+        name = "shadowing.keystore";
+        buildInputs = [ jdk ];
+        phases = ["buildPhase"];
+        buildPhase = ''
+          keytool -genkeypair -validity 1000 -dname "CN=SomeKey,O=SomeOne,C=FR" -keystore $out -storepass '${keypass}' -keypass '${keypass}' -alias SignKey -keyalg RSA -v
+        '';
+      };
+      make-apk = {
+        package,
+        name,
+        classes,
+      } : let 
+        manifest = make-manifest package name;
+      in pkgs.stdenvNoCC.mkDerivation {
+        name = "${package}";
+        buildInputs = [ jdk android-env.androidsdk ];
+        phases = ["buildPhase" "installPhase"];
+        buildPhase = ''
+          mkdir -p build/apk_files
+
+          ${pkgs.lib.strings.concatMapStringsSep "\n" ( item:
+              "cp ${item.drv} build/apk_files/${item.name}"
+          ) classes}
+
+          # link classes.dex not working?
+          # ${build-tools}/aapt2 link -v ---manifest ${manifest}/AndroidManifest.xml -I ${platforms}/android.jar -o build/app.apk build/apk_files/
+
+          ${build-tools}/aapt package -v -f -M ${manifest}/AndroidManifest.xml -I ${platforms}/android.jar -F build/app.apk build/apk_files/
+          ${build-tools}/zipalign -f 4 build/app.apk build/app.aligned.apk
+          ${build-tools}/apksigner sign -ks ${keystore} --v2-signing-enabled true --in build/app.aligned.apk --out build/${package}.apk --ks-pass 'pass:${keypass}'
+        '';
+        installPhase = ''
+          mkdir $out
+          cp build/${package}.apk $out/
+          cp build/${package}.apk.idsig $out/
+        '';
+      };
 
       java-classes-main = pkgs.stdenvNoCC.mkDerivation {
         name = "java-class-main";
@@ -89,35 +128,65 @@
       dummy-classes-dex = java2dex java-classes-dummy;
       empty-classes-dex = java2dex java-classes-empty;
       
-    in rec {
+    in {
 
-      packages = {
-        default = let 
-          manifest = make-manifest "com.example.shadowing.control" "Shadowing C";
-        in pkgs.stdenvNoCC.mkDerivation rec {
-          name = "com-example-shadowing.apk";
-          srcs = self;
-          buildInputs = [ jdk android-env.androidsdk pkgs.which ];
-          phases = ["unpackPhase" "buildPhase" "installPhase"];
-          buildPhase = ''
-            mkdir -p build/apk_files/
-
-            cp ${main-actual-classes-dex} build/apk_files/classes.dex
-
-            # link classes.dex not working?
-            # ${build-tools}/aapt2 link -v ---manifest AndroidManifest.xml -I ${platforms}/android.jar -o build/app.apk build/apk_files/
-
-            ${build-tools}/aapt package -v -f -M ${manifest}/AndroidManifest.xml -I ${platforms}/android.jar -F build/app.apk build/apk_files/
-            ${build-tools}/zipalign -f 4 build/app.apk build/app.aligned.apk
-
-            keytool -genkeypair -validity 1000 -dname "CN=SomeKey,O=SomeOne,C=FR" -keystore build/ToyKey.keystore -storepass 'P@ssw0rd!' -keypass 'P@ssw0rd!' -alias SignKey -keyalg RSA -v
-            ${build-tools}/apksigner sign -ks build/ToyKey.keystore --v2-signing-enabled true --in build/app.aligned.apk --out build/app.signed.apk --ks-pass 'pass:P@ssw0rd!'
-          '';
-          installPhase = ''
-            mkdir $out
-            cp build/app.signed.apk $out/
-            cp build/app.signed.apk.idsig $out/
-          '';
+      packages = rec {
+        control = make-apk {
+          package = "com.example.shadowing.control";
+          name = "Shadowing C";
+          classes = [
+            { name = "classes.dex"; drv = main-actual-classes-dex; }
+          ];
+        };
+        # classes.dex vs classes2.dex
+        shdw1 = make-apk {
+          package = "com.example.shadowing.one";
+          name = "Shadowing 1";
+          classes = [
+            { name = "classes.dex"; drv = main-actual-classes-dex; }
+            { name = "classes2.dex"; drv = dummy-classes-dex; }
+          ];
+        };
+        # classes2.dex vs classes3.dex
+        shdw2 = make-apk {
+          package = "com.example.shadowing.two";
+          name = "Shadowing 2";
+          classes = [
+            { name = "classes.dex"; drv = main-classes-dex; }
+            { name = "classes2.dex"; drv = actual-classes-dex; }
+            { name = "classes3.dex"; drv = dummy-classes-dex; }
+          ];
+        };
+        # classes2.dex vs classes1.dex
+        shdw3 = make-apk {
+          package = "com.example.shadowing.three";
+          name = "Shadowing 3";
+          classes = [
+            { name = "classes.dex"; drv = main-classes-dex; }
+            { name = "classes1.dex"; drv = dummy-classes-dex; }
+            { name = "classes2.dex"; drv = actual-classes-dex; }
+          ];
+        };
+        # classes10.dex vs classes2.dex
+        shdw4 = make-apk {
+          package = "com.example.shadowing.four";
+          name = "Shadowing 4";
+          classes = [
+            { name = "classes.dex"; drv = main-classes-dex; }
+            { name = "classes2.dex"; drv = actual-classes-dex; }
+            { name = "classes3.dex"; drv = empty-classes-dex; }
+            { name = "classes4.dex"; drv = empty-classes-dex; }
+            { name = "classes5.dex"; drv = empty-classes-dex; }
+            { name = "classes6.dex"; drv = empty-classes-dex; }
+            { name = "classes7.dex"; drv = empty-classes-dex; }
+            { name = "classes8.dex"; drv = empty-classes-dex; }
+            { name = "classes9.dex"; drv = empty-classes-dex; }
+            { name = "classes10.dex"; drv = dummy-classes-dex; }
+          ];
+        };
+        default = pkgs.symlinkJoin {
+          name = "all-shadowing-apks";
+          paths = [ control shdw1 shdw2 shdw3 shdw4];
         };
       };
 
diff --git a/test-on-android.sh b/test-on-android.sh
new file mode 100644
index 0000000..1994f68
--- /dev/null
+++ b/test-on-android.sh
@@ -0,0 +1,16 @@
+#!/usr/bin/bash
+
+APK_FOLDER="./result"
+
+adb logcat -s SHADOWING &
+log_pid=$!
+
+for pkg in $(ls ${APK_FOLDER} | grep '.apk$' | sed 's/.apk$//'); do
+  adb install "${APK_FOLDER}/${pkg}.apk" &> /dev/null
+  sleep 2
+  adb shell am start -n "${pkg}/com.example.shadowing.MainActivity" &> /dev/null
+  sleep 2
+  adb uninstall "${pkg}" &> /dev/null
+done
+
+kill "${log_pid}"