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TrivialKart

A sample game demonstrating use of Google Play technologies on Android with the Unity engine.

This verson of TrivialKart demonstrates:

  • In-app purchases through Google Play using the Unity IAP system
  • Play Games Services, for signin, achievements, leaderboards, friends and cloud save
  • Play Integrity for receiving integrity signals about device integrity and Play license status
  • The Input SDK for Google Play Games for PC

Pre-requisites

  • Unity 2020 LTS or higher with Android build support (Play plugins are compatible with earlier versions of Unity, but the TrivialKart project is built using 2020 LTS)

Pre-requsities for enabling Google Play features

  • Google Play developer account

Getting started

Open the project in Unity and open the TrivialKartScene file from Assets/Scenes.

By default, Google Play featues are disabled. The scene be run in-editor or exported to device and run. With in-app purchase integration disabled, all prices are placeholder and purchasing in-game items automatically succeeds.

Overview

In TrivialKart, the player has a vehicle which they can drive by tapping on it. Driving the car uses gas. When the car runs out of gas, to continue driving, more must be purchased using in-game currency. If the player runs out of in-game currency, they may buy more via in-app purchases. In-game currency is an example of a consumable purchase that may be repeated.

The game has different cars available for unlock. One car is purchasable using in-game currency; other cars require unlocking via in-app purchase. These unlocks are permanent one-time purchases.

The game also has subscriptions available for in-app purchase. One subscription unlocks a different travel background. A second, more expensive subscription unlocks the travel background and adds a 40% discount off the cost of purchasing gas or unlocks using in-game currency. The features of a subscription are only available if the subscription is active.

Enabling in-app purchases

Creating a project in the Google Play Developer Console

  1. Go to the Google Play Developer Console and create a new application.
  2. Select the Monetization setup page for your new application. Copy the Base64-encoded public key text in the Licensing area. You will need to use this key when configuring Unity IAP.

Updating the package name in Unity

  1. In Unity, if you haven't already, select File -> Build Settings... from the Unity menu bar and switch the platform to Android.
  2. From the Build Settings window, select the Player Settings... button.
  3. In the Player Settings window, expand the Other Settings section and enter the application package identifer you specified in the Play Console in the Package Name field.

Enabling Unity IAP

Follow the instructions at Setting up Unity IAP

This sample was tested using version 4.1.2 of the Unity In App Purchasing package installed through the Package Manager. We recommend this as a minimum version for this sample. Use of earlier versions, or the older version of Unity IAP available on the Unity Asset Store is not supported.

Setting up receipt obfuscation

NOTE If the Services menu does not appear in your Unity menu bar, try uninstalling and reinstalling the In App Purchasing package from the Unity Package Manager.

  1. Select Services -> Unity IAP -> Receipt Validation Obfuscation from the Unity menu bar.
  2. Paste the Base64-encoded public key you retrieved from the Google Play Developer console into the text box.
  3. Click the Obfuscate Google Play License Key button.
  4. Close the popup window.

Turning on IAP in the project

  1. From the Unity menu bar, select TrivialKart -> BuildOptions -> Build with IAP

This menu item acts as a global toggle, if unchecked NO_IAP is defined in the Scripting Define Symbols. If checked USE_IAP is defined in the Scripting Define Symbols.

Building and uploading a signed build

  1. In the Unity Build Settings window, make sure the TrivialKart/Scenes/playScene is added to the list of Scenes In Build.
  2. Configure the project for signing by creating a new key store at File > Build Settings > Player Settings > Publishing Settings. Additional instructions on configurating signing are available. on the Unity site.
  3. Build an App Bundle.
  4. Use the Google Play Developer Console to upload your build to Google Play. You can upload to the Internal test track.

Setting up the purchase items in Google Play

Note: you must upload a build to Google Play to be able to create your in-app purchasing items in the Google Play Developer Console Console.

  1. Return to the Google Play Developer Console.

  2. Under Monetize -> Products -> In-app products, create the following in-app products:

    Product ID Price
    car_offroad $2.99
    car_kart $4.99
    five_coins $0.99
    ten_coins $1.99
    twenty_coints $2.49
    fifty_coins $4.99

  3. Under Monetize -> Products -> Subscriptions, create subscriptions with these IDs and prices (Fill out the other fields. Set them to "Active"):

    Product ID Price
    silver_subscription $1.99
    golden_subscription $4.99

  4. Publish your build to the testing channel. It may take up to a few hours to process the build. Running a build before processing complete can result in errors such as Google Play reporting that "this version of the application is not enabled for in-app billing".

  5. Add tester accounts to your game. This will allow you to test purchases and subscriptions without being charged. Test accounts also have greatly reduced subscription periods, allowing for easier testing of subscription features.

Enabling Play Games Services

Enable Play Games Services in Play Console

Follow the instructions for setting up Play Games Services for your app in the Play Console.

You will also need to enable save games since TrivialKart uses the Cloud Save feature.

Defining the leaderboard and achievements

In the Play Games Services section of your Play Console entry for your app, access the Achievements and Leaderboard sections to add the following achievements and leaderboard:

Achievements Name: tk_achievement_drive Description: Drive a while Initial State: Revealed Incremental: Unchecked Points: 5

Name: tk_achievement_truck Description: Unlock the truck Initial State: Revealed Incremental: Unchecked Points: 5

Leaderboards Name: tk_leaderboard_distance Format: Number Number of decimals 2 Sort order: Largest first

Make sure to publish your achievements and leaderboard after creation.

Setup the Unity plugin

  1. Download version 11.0 or later of the Play Games Services for Unity plugin from its GitHub releases page.
  2. Extract the .zip file.
  3. Install the .unitypackage file located in the current-build directory of the extracted archive using Assets > Import Package > Custom Package.

Generate Google Play Games constants

  1. From the Play Console entry for your app, select Play Games Services -> Setup and management -> Achievements.
  2. Find the Get resources button and click it.
  3. Copy the text from the Android (XML) tab.
  4. From the Unity menu bar, select Window -> Google Play Games -> Setup -> Android Setup....
  5. Paste the resource text into the Resources Definition field.
  6. Click the Setup button

Configure Proguard

  1. Go to File > Build Settings > Player Settings and click Publishing Settings section.
  2. Choose Proguard for Minify > Release. Then, enable User Proguard File.
  3. If you want the plugin to be proguarded for debug apks as well, you can repeat for Proguard for Minify > Debug.
  4. Copy the contents of the proguard configuration file at Assets/GooglePlaygames/com.google.play.games/Proguard/games.txt into Assets/Plugins/Android/proguard-user.txt.

Enable in the Play Games Services feature in the Unity Editor

From the Unity menu bar, select TrivialKart -> BuildOptions -> Build with Google Play Games Services

Adding the upload key for local build testing

Builds published for testing or distribution on Google Play are resigned by Google. When you configure Play Games Services, these keys are used for authentication. If you run a locally built APK signed with your upload key, Play Games Services won't be able to authenticate. To fix this, you can add the upload key to a new OAuth client for your local builds. To do this:

  1. In Play Console, go to Setup->App Integrity
  2. Select the App Signing tab
  3. Find the Upload key certificate section and copy the SHA-1 certificate fingerprint
  4. Go to Grow->Play Games Services->Setup and Management->Configuration
  5. Find the Credentials section and click on Add Credentials
  6. Give the credential a different name from the existing name
  7. Click Create OAuth Client and follow the instructions, using the SHA-1 certificate fingerprint from the Upload key
  8. Click Refresh OAuth clients until the new client is listed in the OAuth client list
  9. Select the new client from the list and click Save changes
  10. Return to the Configuration screen and click Review and publish
  11. On the next screen, click Publish

Enabling Play Integrity

Play Console setup

See the Play Integrity guide for information on configuring Play Integrity in the Google Play Console.

Downloading the plugin

You will need to download the unitypackage file for Play Integrity from the Google Play Unity plugins releases page.

After downloading the plugin, install it using using Assets > Import Package > Custom Package.

Server specifications

The Play Integrity code requires communication with a backend server to:

  • Generate a nonce
  • Decrypt the integrity verdict

You can find implementation details for these tasks in the Work with integrity verdicts guide.

A server implementation is not included with this sample. You can build and deploy a server using the framework and platform of your choice. TrivialKart expects the server to define two endpoints accessed via HTTP requests:

A getNonce endpoint, accessed via a GET request. This URL returns a json payload containing the nonce value. The JSON payload containts a single key/value pair with the key being nonce.

A processToken endpoint, accessed via a POST request. The URL expects a JSON payload containing the encrypted integrity token returned by the Play Integrity plugin. The JSON payload contains a single key/value pair with the key being tokenString. The POST request returns a JSON payload containing the integrity verdict information. This is serialized into the structures defined in the IntegrityVerdict.cs source file.

Configuring server URLs

You will need to customize the following lines in PlayIntegrityController.cs to point to the URLs for your server:

private readonly string URL_GETNONCE = "https://your-play-integrity-server.com/getNonce"; private readonly string URL_PROCESSTOKEN = "https://your-play-integrity-server.com/processToken";

Enable the Play Integrity feature in the Unity Editor

From the Unity menu bar, select TrivialKart -> BuildOptions -> Build with Play Integrity

Verdict display in game

An integrity verdict is requested when opening the store page. A verdict will only be requested once per play session. The summary results string is displayed near the top of the store page.

Note that in a real game, you would not directly return the decrypted verdict information, but communicate the results in a way that makes sense for your game. For simplicity, this sample expects the raw verdict json.

Building for Google Play Games

  1. Enable x86 ABI architecture. This can be activated using Player Settings > Other Settings > Target Architectures and enabling both x86 (Chrome OS) and x86-64 (Chrome OS). Note: You can only enable x86 support when using the IL2CPP Scripting Backend. This can be done from Player Settings > Configuration > Scripting Backend > IL2CPP.
  2. Disable unsupported android features and permissions. This can be done by adding custom build logic to your AndroidManifest.xml. To do this, open Player Settings > Publishing Settings and find the Build section. Then, enable the Custom Main Manifest or corresponding manifest for the feature or permission you need to disable. At this point, you can find that manifest and add android:required="false" to the <uses-feature> or uses-permission declaration for all features that Google Play Games does not support. For more information, see the Unity documention on Android Manifests. You should also disable any lines requesting permissions in your Unity code. See the Unity documentation on requestion permissions for more details.
  3. Install the Input SDK Unity package using Assets > Import Package > Custom Package.
  4. From the Unity menu bar, select TrivialKart > BuildOptions > Build for Google Play Games PC to enable the appropriate scripting defines.
  5. Create a build using the normal Unity build process.

Support

If you've found any errors or bugs in this sample game, please file an issue.

This is not an officially supported Google product.

Build version workarounds

If you forget to select the version you want to build before closing Unity, you may be unable to see the TrivialKart > BuildOptions menu. To fix it, delete the directives under Edit > Project Settings > Player > Other Settings > Script Compilation and restart Unity.

Further reading

CHANGELOG

2022-04-01: 1.1.0 - Added Play Games Services, Play Integrity and Google Play Games for PC features. 2022-01-27: 1.0.0 - Initial release.

Graphical asset credits and license

The PNG and font graphic asset files used in TrivalKart are from Kenney's game assets. These files are licensed under a Creative Commons Zero license.