diff --git a/.gitignore b/.gitignore
index d04b274..1ffd713 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,4 +14,4 @@
 .cxx
 local.properties
 
-gradle.properties
+apikeys.properties
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..8a29d56
--- /dev/null
+++ b/README.md
@@ -0,0 +1,17 @@
+
+# How Long To Beat Demo App
+
+
+## Building
+
+### Create apikeys.properties
+
+Add the following to a new file called `apikeys.properties` (in the root folder):
+
+```
+GoogleVisionApiKey="yourkey"
+```
+
+Your Google Vision API Key can be fetched through [console.cloud.google.com](https://console.cloud.google.com).
+
+The key `GoogleVisionApiKey` is used in `build.gradle.kts` of the app and auto-generates the correct string in the class `BuildConfig`, ready to be used in the Kotlin/Java code. See The app Gradle build file for more information. 
\ No newline at end of file
diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index bff1e36..6cfa2f9 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -5,6 +5,11 @@ plugins {
     kotlin("plugin.serialization") version "1.5.21"
 }
 
+val apiKeys = file("../apikeys.properties").readLines().map {
+    val keyvalues = it.split("=")
+    keyvalues[0] to keyvalues[1]
+}.toMap()
+
 android {
     compileSdk = 31
     buildToolsVersion = "31.0.0"
@@ -28,6 +33,13 @@ android {
             )
         }
     }
+
+    buildTypes.forEach {
+        // Will crash and do weird things if you did not provide your key.
+        // See README.md for more information.
+        it.buildConfigField("String", "GOOGLE_VISION_API_KEY", apiKeys["GoogleVisionApiKey"]!!)
+    }
+
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_1_8
         targetCompatibility = JavaVersion.VERSION_1_8
@@ -58,7 +70,6 @@ dependencies {
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.5.1")
 
     // --- navigation
-    // see https://developer.android.com/guide/navigation/navigation-getting-started
     val nav_version = "2.3.5"
     implementation("androidx.navigation:navigation-fragment:$nav_version")
     implementation("androidx.navigation:navigation-ui:$nav_version")
@@ -79,16 +90,7 @@ dependencies {
     // --- Volley for HTTP requests
     implementation("com.android.volley:volley:1.2.0")
 
-    // --- Google Vision API specific dependencies
-    // firebase specific
-    //implementation("com.google.firebase:firebase-bom:28.3.1")
-
-    // OAUth play services
-    //implementation("com.google.android.gms:play-services-auth:19.2.0")
-    //implementation("com.google.android.gms:play-services-base:17.6.0")
-
-
-    // Vision itself
+    // Google Vision
     // comes with conflicts, exclude http client using https://docs.gradle.org/current/userguide/dependency_downgrade_and_exclude.html
     implementation("com.google.api-client:google-api-client-android:1.32.1") {
         exclude(module = "httpclient")
diff --git a/app/src/main/java/be/kuleuven/howlongtobeat/google/GoogleVisionClient.kt b/app/src/main/java/be/kuleuven/howlongtobeat/google/GoogleVisionClient.kt
index e71f39b..86b2e28 100644
--- a/app/src/main/java/be/kuleuven/howlongtobeat/google/GoogleVisionClient.kt
+++ b/app/src/main/java/be/kuleuven/howlongtobeat/google/GoogleVisionClient.kt
@@ -1,6 +1,7 @@
 package be.kuleuven.howlongtobeat.google
 
 import android.graphics.Bitmap
+import be.kuleuven.howlongtobeat.BuildConfig
 import be.kuleuven.howlongtobeat.ImageRecognizer
 import be.kuleuven.howlongtobeat.asEncodedGoogleVisionImage
 import be.kuleuven.howlongtobeat.cartridges.Cartridge
@@ -17,13 +18,9 @@ import kotlinx.coroutines.withContext
 
 class GoogleVisionClient : ImageRecognizer {
 
-    // TODO encrypt and store externally: https://cloud.google.com/docs/authentication/api-keys?hl=en&visit_id=637642790375688006-1838986332&rd=1
-    private val vision = Vision.Builder(NetHttpTransport(), GsonFactory.getDefaultInstance(), null)
-        .setVisionRequestInitializer(VisionRequestInitializer("AIzaSyCaMjQQOY7508y95riDhr25fsrqe3m2JW0"))
-        .setApplicationName("How Long To Beat")
-        .build()
-
     private suspend fun findCartCodeViaGoogleVision(cameraSnap: Bitmap): String? {
+        val vision = buildVisionClient()
+
         var response: BatchAnnotateImagesResponse
         withContext(Dispatchers.IO) {
             val sml2Data = cameraSnap.asEncodedGoogleVisionImage()
@@ -50,7 +47,16 @@ class GoogleVisionClient : ImageRecognizer {
         val gbId = response.responses.get(0).textAnnotations.filter {
             Cartridge.isValid(it.description)
         }.firstOrNull()
-        return gbId?.description ?: null
+        return gbId?.description
+    }
+
+    private fun buildVisionClient(): Vision {
+        assert(BuildConfig.GOOGLE_VISION_API_KEY.length > 1)
+
+        return Vision.Builder(NetHttpTransport(), GsonFactory.getDefaultInstance(), null)
+            .setVisionRequestInitializer(VisionRequestInitializer(BuildConfig.GOOGLE_VISION_API_KEY))
+            .setApplicationName("How Long To Beat")
+            .build()
     }
 
     override suspend fun recognizeCartCode(image: Bitmap): String? = findCartCodeViaGoogleVision(image)
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 0000000..cac7c68
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1,21 @@
+# Project-wide Gradle settings.
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+# org.gradle.parallel=true
+# AndroidX package structure to make it clearer which packages are bundled with the
+# Android operating system, and which are packaged with your app"s APK
+# https://developer.android.com/topic/libraries/support-library/androidx-rn
+android.useAndroidX=true
+# Automatically convert third-party libraries to use AndroidX
+android.enableJetifier=true
+# Kotlin code style for this project: "official" or "obsolete":
+kotlin.code.style=official