BlogTry Replay
Back to Blog
January 6, 202610 min readBuilding a Real-time

Building a Real-time Multiplayer Game UI with Replay AI and Phaser.js

R
Replay Team
Developer Advocates

TL;DR: Replay's behavior-driven reconstruction enables rapid prototyping of real-time multiplayer game UIs from video demonstrations, significantly reducing development time and complexity.

Building a Real-time Multiplayer Game UI with Replay and Phaser.js#

Creating engaging user interfaces for real-time multiplayer games is notoriously challenging. You need to handle complex state management, synchronization, and responsiveness, all while delivering a seamless player experience. Traditional UI development often involves tedious manual coding, extensive debugging, and iterative design refinements. But what if you could significantly accelerate this process by leveraging AI to understand and reconstruct UI behavior from video?

This is where Replay comes in. Replay is a revolutionary video-to-code engine that uses Gemini to reconstruct working UI from screen recordings. Unlike screenshot-to-code tools that only capture visual elements, Replay analyzes video to understand user behavior and intent. This "Behavior-Driven Reconstruction" approach allows you to rapidly prototype and iterate on your game UI based on real-world usage patterns. In this article, we'll explore how to use Replay to build a real-time multiplayer game UI with Phaser.js, a popular JavaScript game framework.

Why Video-to-Code for Game UI?#

Traditional UI development for games is often a bottleneck. Manually coding UI elements, wiring up event handlers, and ensuring smooth transitions can consume significant development time. Video-to-code offers a compelling alternative by allowing you to:

  • •Rapidly Prototype: Quickly generate initial UI layouts and functionality from video demonstrations.
  • •Iterate Efficiently: Easily modify and refine the generated code based on user feedback and testing.
  • •Focus on Gameplay: Free up development resources to focus on core game mechanics and features.
  • •Visualize Complex Interactions: Capture intricate UI interactions and workflows in video, and let Replay translate them into functional code.

Replay vs. Traditional UI Development#

The following table highlights the key differences between using Replay and traditional UI development approaches:

FeatureTraditional UI DevelopmentReplay
InputManual codingVideo recording
Learning CurveHighLow
Iteration SpeedSlowFast
Behavior AnalysisManualAutomatic (Behavior-Driven)
Code QualityVariableConsistent, based on video behavior
Initial Setup TimeLongShort

Setting up Phaser.js and a Basic Multiplayer Environment#

Before diving into Replay, let's set up a basic Phaser.js project and a simple multiplayer environment using Socket.IO.

Step 1: Project Setup

Create a new directory for your project and initialize a Node.js project:

bash
mkdir phaser-replay-game
cd phaser-replay-game
npm init -y

Install Phaser.js and Socket.IO:

bash
npm install phaser socket.io

Step 2: Basic Server Setup (server.js)

Create a

text
server.js
file to handle Socket.IO connections:

javascript
// server.js
const express = require('express');
const http = require('http');
const socketIO = require('socket.io');
const path = require('path');

const app = express();
const server = http.createServer(app);
const io = socketIO(server);

app.use(express.static(path.join(__dirname, 'public')));

io.on('connection', (socket) => {
  console.log('User connected:', socket.id);

  socket.on('disconnect', () => {
    console.log('User disconnected:', socket.id);
  });
});

const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

Step 3: Client-Side Setup (public/index.html)

Create a

text
public
directory and add an
text
index.html
file:

html
<!DOCTYPE html>
<html>
<head>
    <title>Phaser + Replay</title>
    <style>
        body { margin: 0; }
        canvas { display: block; margin: 0 auto; }
    </style>
</head>
<body>
    <script src="/socket.io/socket.io.js"></script>
    <script src="phaser.min.js"></script>
    <script src="game.js"></script>
</body>
</html>

Download the Phaser.js library (phaser.min.js) from the official Phaser website and place it in the

text
public
directory.

Step 4: Basic Phaser Game (public/game.js)

Create a

text
game.js
file to initialize Phaser and set up a basic scene:

javascript
// public/game.js
const config = {
    type: Phaser.AUTO,
    width: 800,
    height: 600,
    scene: {
        preload: preload,
        create: create,
        update: update
    }
};

const game = new Phaser.Game(config);
let player;

function preload () {
    this.load.image('player', 'player.png'); // Replace with your player image
}

function create () {
    player = this.add.image(400, 300, 'player');
}

function update () {
    // Placeholder for player movement and game logic
}

Replace

text
player.png
with an actual image file. You can use any small image for testing.

📝 Note: This is a minimal setup. A full multiplayer game would require more sophisticated server-side logic, state management, and synchronization mechanisms.

Using Replay to Generate the Game UI#

Now, let's integrate Replay to generate our game UI. Imagine you want to create a simple UI with a score display, a health bar, and a chat window.

Step 1: Record a Video Demonstration

Record a video demonstrating the desired UI behavior. This video should showcase:

  • •The initial layout of the UI elements.
  • •How the score updates when a "score" button is clicked.
  • •How the health bar decreases when a "damage" button is clicked.
  • •How text is entered and sent in the chat window.

Be clear and deliberate in your actions during the recording. The more precise your demonstration, the better Replay can understand and reconstruct the UI.

💡 Pro Tip: Narrate your actions while recording the video. This provides additional context for Replay and improves the accuracy of the code generation.

Step 2: Upload the Video to Replay

Upload the recorded video to the Replay platform. Replay will analyze the video using its AI-powered engine and generate the corresponding code.

Step 3: Review and Refine the Generated Code

Replay will generate code snippets that you can integrate into your Phaser.js project. Review the generated code and make any necessary adjustments to ensure it aligns with your desired functionality.

For example, Replay might generate code for the score display like this:

javascript
// Generated by Replay
let score = 0;
let scoreText;

function create() {
  // ... other create logic ...
  scoreText = this.add.text(16, 16, 'Score: 0', { fontSize: '32px', fill: '#fff' });

  const scoreButton = this.add.dom(100, 500, 'button', 'width: 100px; height: 40px; font-size: 20px', 'Score +1');
  scoreButton.addListener('click');
  scoreButton.on('click', () => {
    score += 1;
    scoreText.setText('Score: ' + score);
  });
}

And for the health bar:

javascript
// Generated by Replay
let health = 100;
let healthBar;

function create() {
  // ... other create logic ...
  healthBar = this.add.graphics();
  healthBar.fillStyle(0x00ff00, 1);
  healthBar.fillRect(16, 50, health, 20);

  const damageButton = this.add.dom(250, 500, 'button', 'width: 100px; height: 40px; font-size: 20px', 'Damage -10');
  damageButton.addListener('click');
  damageButton.on('click', () => {
    health -= 10;
    health = Math.max(0, health); // Ensure health doesn't go below 0
    healthBar.clear();
    healthBar.fillStyle(0x00ff00, 1);
    healthBar.fillRect(16, 50, health, 20);
  });
}

And for the chat window (this will require more manual integration with Socket.IO):

javascript
// Generated by Replay (requires Socket.IO integration)
const chatInput = document.createElement('input');
chatInput.style.position = 'absolute';
chatInput.style.left = '16px';
chatInput.style.bottom = '16px';
chatInput.style.width = '300px';
chatInput.style.height = '30px';

const sendButton = document.createElement('button');
sendButton.style.position = 'absolute';
sendButton.style.left = '320px';
sendButton.style.bottom = '16px';
sendButton.style.width = '80px';
sendButton.style.height = '30px';
sendButton.textContent = 'Send';

document.body.appendChild(chatInput);
document.body.appendChild(sendButton);

sendButton.addEventListener('click', () => {
  const message = chatInput.value;
  socket.emit('chatMessage', message); // Assuming 'socket' is your Socket.IO connection
  chatInput.value = '';
});

// ... Socket.IO message handling (example) ...
socket.on('chatMessage', (message) => {
  const chatLog = document.createElement('div');
  chatLog.textContent = message;
  document.body.appendChild(chatLog); // Simple chat log append
});

⚠️ Warning: The chat window example requires manual integration with Socket.IO to handle real-time messaging. Replay can generate the UI elements and event handlers, but you'll need to connect it to your multiplayer backend.

Step 4: Integrate and Test

Integrate the generated code into your

text
game.js
file. You'll likely need to adjust positioning, styling, and event handling to fit your specific game requirements. Test thoroughly to ensure the UI functions as expected in a multiplayer environment.

Key Benefits of Using Replay for Game UI#

  • •Accelerated Development: Significantly reduce the time required to create and iterate on game UIs.
  • •Improved Accuracy: Leverage AI-powered behavior analysis to generate code that accurately reflects your intended UI functionality.
  • •Enhanced Collaboration: Easily share video demonstrations with designers and developers to facilitate communication and feedback.
  • •Reduced Costs: Lower development costs by automating UI generation and reducing manual coding efforts.

Common Challenges and Solutions#

  • •Complex Interactions: For highly complex UI interactions, you may need to break down the video demonstration into smaller, more manageable segments.
  • •Edge Cases: Ensure your video covers a wide range of scenarios and edge cases to generate robust and reliable code.
  • •Styling and Customization: Replay can generate the basic UI structure and functionality, but you may need to manually adjust the styling and customization to match your game's aesthetic.
  • •Multiplayer Synchronization: Replay focuses on UI generation. You'll still need to handle multiplayer synchronization and state management using appropriate networking technologies.

Real-World Use Cases#

  • •Rapid Prototyping: Quickly create mockups and prototypes of game UIs to test different design concepts.
  • •UI Redesign: Generate code for redesigned UI elements based on video demonstrations of the desired changes.
  • •Tutorial Creation: Create interactive tutorials by recording video demonstrations of gameplay and generating code for the tutorial UI elements.
  • •Accessibility Improvements: Identify and address accessibility issues by recording video demonstrations of users interacting with the UI and generating code for accessibility enhancements.

Replay's Core Features#

Replay offers a range of features designed to streamline UI development:

  • •Multi-Page Generation: Generate code for multi-page UIs from a single video recording.
  • •Supabase Integration: Seamlessly integrate with Supabase for backend data storage and management.
  • •Style Injection: Easily inject custom styles into the generated code to match your game's design.
  • •Product Flow Maps: Visualize the flow of user interactions within the UI.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited usage. Paid plans are available for higher usage and access to advanced features.

How is Replay different from v0.dev?#

While v0.dev uses text prompts to generate UI components, Replay analyzes video recordings to understand user behavior and reconstruct UI functionality based on visual demonstrations. Replay focuses on behavior-driven reconstruction, which is particularly valuable for capturing complex interactions and workflows. Replay understands what users are trying to do, not just what they see.

Can Replay handle complex animations and transitions?#

Replay can capture basic animations and transitions demonstrated in the video recording. However, for more complex animations, you may need to manually implement them using Phaser.js animation features.

What types of games is Replay suitable for?#

Replay can be used for a wide range of game genres, including RPGs, strategy games, puzzle games, and action games. It is particularly well-suited for games with complex UIs and intricate interactions.

How does Replay handle dynamic data?#

Replay can generate code for displaying dynamic data, but you'll need to connect the generated UI elements to your game's data sources and update them accordingly.

Ready to try behavior-driven code generation? Get started with Replay - transform any video into working code in seconds.

Ready to try Replay?

Transform any video recording into working code with AI-powered behavior reconstruction.

Launch Replay Free