diff --git a/README.md b/README.md
index 499fc9d82..75a7e90c1 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,16 @@ RoboTutor uses a large volume of external assets at runtime.  To successfully ru
 
 3. You may need to install different versions of the build tools and SDKs.
 
-4. There are a number of build variants you can select to generate versions that support static language selections and also vesions that permit dynamic language selection at runtime.
+4. add a file named "keystore.properties" to your root project directory, and give it the following contents
+```
+storePassword=xxx
+keyPassword=xxx
+keyAlias=xxx
+storeFile=/Users/
+```
+
+
+5. There are a number of build variants you can select to generate versions that support static language selections and also vesions that permit dynamic language selection at runtime. In order to generate any flavor that depends on the key signature, you must generate your own keystore.
 
 
 
diff --git a/comp_counting/build.gradle b/comp_counting/build.gradle
index 46cebf96c..b9bb7073d 100644
--- a/comp_counting/build.gradle
+++ b/comp_counting/build.gradle
@@ -1,14 +1,14 @@
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 25
-    buildToolsVersion "25.0.3"
+    compileSdkVersion rootProject.ext.rtCompileSdkVersion
+    buildToolsVersion rootProject.ext.rtBuildToolsVersion
 
     defaultConfig {
-        minSdkVersion 21
-        targetSdkVersion 25
-        versionCode 1
-        versionName "1.0"
+        minSdkVersion rootProject.ext.rtMinSdkVersion
+        targetSdkVersion rootProject.ext.rtTargetSdkVersion
+        versionCode rootProject.ext.rtVersionCode
+        versionName rootProject.ext.rtVersionName
 
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
 
diff --git a/comp_counting2/build.gradle b/comp_counting2/build.gradle
index 862717bbb..754e95f56 100644
--- a/comp_counting2/build.gradle
+++ b/comp_counting2/build.gradle
@@ -6,10 +6,10 @@ android {
 
 
     defaultConfig {
-        minSdkVersion 21
-        targetSdkVersion 25
-        versionCode 1
-        versionName "1.0"
+        minSdkVersion rootProject.ext.rtMinSdkVersion
+        targetSdkVersion rootProject.ext.rtTargetSdkVersion
+        versionCode rootProject.ext.rtVersionCode
+        versionName rootProject.ext.rtVersionName
 
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
 
diff --git a/comp_logging/build.gradle b/comp_logging/build.gradle
index 5871be0c6..8a6345e70 100644
--- a/comp_logging/build.gradle
+++ b/comp_logging/build.gradle
@@ -5,10 +5,10 @@ android {
     buildToolsVersion "25.0.2"
 
     defaultConfig {
-        minSdkVersion 21
-        targetSdkVersion 25
-        versionCode 1
-        versionName "1.0"
+        minSdkVersion rootProject.ext.rtMinSdkVersion
+        targetSdkVersion rootProject.ext.rtTargetSdkVersion
+        versionCode rootProject.ext.rtVersionCode
+        versionName rootProject.ext.rtVersionName
 
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"