Chris Schalk presented on PlayN, an open source and cross-platform game abstraction layer. PlayN allows developers to write core game code in a platform agnostic way using Java. It then compiles the code to run on multiple platforms including HTML5, Android, and Flash. PlayN handles common game components like input handling, images, and resource loading so developers can focus on game logic. It also includes a built-in physics engine. Using PlayN and Google Web Toolkit, developers can write games once in Java and deploy them to different platforms, improving performance through optimizations like code size reduction and caching.

1. Chris Schalk
Google Developer Advocate
Creación de video juegos en la
nube
(How to Build Kick Ass Games in the Cloud)

2. Let's start with a Demo!

3. Introducing PlayN!
An abstraction layer for games (Formerly ForPlay)
● A small API for building fast cross-platform games
● Core game code can be platform agnostic
● Develop games in Java
○ Familiar language/toolset
● Is compatible with GWT
○ Compiles to JS/HTML5, (among other platforms)
● Free and Open Source (alpha)
○ http://code.google.com/p/playn

4. Introducing PlayN!
A GWT abstraction layer for games
PlayN API
Implementations for Java, HTML5(GWT/JS), Android, Flash

5. Components of PlayN!
Implements core.Game PlayN.*
Fully generic gaming components. Core game logic is fully platform
independent!

6. Components of PlayN!
Just implement PlayN.core.Game

7. Components of PlayN!
public void OnPointerMove( Pointer.Event event ) {
public void OnPointerEnd( Pointer.Event event
) {
public void OnKeyDown( keyboard.Event event
) {
Easy to write code to handle common input devices

8. Components of PlayN!
Images are handled via the PlayN Layering system

9. Components of PlayN!
Game resources are preloaded using the assetManager

10. Time for some more demos!

11. PlayN Cross Platform Magic
● Game uses core PlayN abstractions, is unaware of which
platform is running
● The only platform-specific code is in the entry point for
each platform:
PlayN.run(new MyGame()); PlayN.run(new MyGame());

12. Other PlayN Benefits
● Built-in physics engine based on proven OpenSource
technologies
● Box2D
○ C++ 2D Physics engine by Erin Catto
● JBox2D
○ A port of Box2D from C++ to Java
● GWTBox2D
○ A port of JBox2D from Java to JavaScript

13. Benefits of GWT Abstraction
● GWT Compiler optimizes code for size
○ Removes unused code
○ Evaluates when possible at compile time
○ Inlines functions
○ Heavily obfuscated result code
● Smaller compiled code - faster load time
● Optimized caching, avoids unnecessary network IO

14. Benefits of HTML5 for Games
● New HTML elements
○ 2D canvas
○ Audio, Video
● Application Cache
● 3D Canvas (WebGL)
○ Open GL ES 2.0 made JavaScript friendly
● CSS3
○ Supports hardware accelerated transforms

15. More demos
● Building your own games
○ Introducing
"App Engine: Cloud Warrior"

16. App Engine Cloud Warrior
Architecture
App Engine Google Storage
Datastore
Game Assets
(images/sounds)
Game Scores
Profile Data
Game Play
(PlayN)

17. PlayN Summary
● Open source, cross-platform game abstraction layer
○ Core game logic is platform agnostic
● ForPlay abstracts away the core components of a game
○ The game loop, I/O system, and asset management
● Write in familiar Java, get performance on multiple
platforms
○ Superior Java development/debug
○ GWT allows compilation to fast JavaScript/HTML5
● Your assignment:
○ Download PlayN and build a game!
○ http://code.google.com/p/playn/

18. Q&A
@cschalk