Promo Video

Promo Video Recording

Record smooth, autonomous promo footage of a Phaser game for marketing / social media. The output is a 50 FPS MP4 in mobile portrait (9:16) — ready for TikTok, Reels, Moltbook, or X.

Technique

Playwright's recordVideo caps at 25 FPS with no config option. We work around it:

1. Slow the game to 0.5× by patching all 5 Phaser time subsystems
2. Record for 2× the desired duration at Playwright's native 25 FPS
3. FFmpeg speed-up 2× → effective 50 FPS output

Prerequisites

• Playwright — must be installed (npm install -D @playwright/test && npx playwright install chromium)
• FFmpeg — must be available on PATH (brew install ffmpeg on macOS)
• Dev server running — game must be served on localhost

Check both before starting:

npx playwright --version
ffmpeg -version | head -1

If FFmpeg is not found, warn the user and skip the promo video step (it's non-blocking — the game still works without it).

Capture Script — Game-Specific Adaptation

Every game gets a custom scripts/capture-promo.mjs. The subagent must read the game's source files to determine:

1. Death/Failure Patching (CRITICAL)

The video must show continuous gameplay — never game over. Read GameScene.js (or equivalent) to find the death/failure method and monkey-patch it out.

How to find it: Search for the method called on collision/death. Common patterns:

• this.triggerGameOver() — dodge games
• this.takeDamage() → this.lives <= 0 — multi-life games
• this.gameOver() — direct call
• eventBus.emit(Events.PLAYER_HIT) / eventBus.emit(Events.GAME_OVER) — event-driven

Patch template (adapt per game):

await page.evaluate(() => {
  const scene = window.__GAME__.scene.getScene("GameScene");
  if (scene) {
    // Patch ALL paths to game over
    scene.triggerGameOver = () => {};
    scene.onPlayerHit = () => {};
    // For multi-life games, also prevent damage:
    // scene.takeDamage = () => {};
    // scene.playerDied = () => {};
  }
});

2. Input Sequence Generation

The video must show dynamic, natural-looking gameplay. Read the game's input handling to determine:

• Which keys — ArrowLeft/ArrowRight? Space? WASD? Mouse clicks?
• Input style — continuous hold (movement), tap (jump/shoot), or both?
• Movement pattern — should the player sweep across the screen, dodge reactively, jump rhythmically?

Input patterns by game type:

Randomize timing to avoid robotic-looking movement:

const holdMs = 150 + Math.floor(Math.random() * 450);
const pauseMs = 50 + Math.floor(Math.random() * 250);

Add a pause at the start (1-2s) to let the entrance animation play — this is the hook.

3. Game Boot Detection

All Phaser games built with the /viral-game or /make-game pipelines expose these globals:

• window.__GAME__ — Phaser.Game instance
• window.__GAME_STATE__ — GameState singleton
• window.__EVENT_BUS__ — EventBus singleton

Wait for both boot and active gameplay:

await page.waitForFunction(() => window.__GAME__?.isBooted, { timeout: 15000 });
await page.waitForFunction(() => window.__GAME_STATE__?.started, {
  timeout: 10000,
});

4. Time Scaling Injection

Slow all 5 Phaser time subsystems for the recording:

await page.evaluate(
  ({ factor }) => {
    const game = window.__GAME__;
    const scene = game.scene.getScene("GameScene");

    // 1. Update delta — slows frame-delta-dependent logic
    const originalUpdate = scene.update.bind(scene);
    scene.update = function (time, delta) {
      originalUpdate(time, delta * factor);
    };

    // 2. Tweens — slows all tween animations
    scene.tweens.timeScale = factor;

    // 3. Scene timers — slows scene.time.addEvent() timers
    scene.time.timeScale = factor;

    // 4. Physics — slows Arcade/Matter physics
    // NOTE: Arcade physics timeScale is INVERSE (higher = slower)
    if (scene.physics?.world) {
      scene.physics.world.timeScale = 1 / factor;
    }

    // 5. Animations — slows sprite animation playback
    if (scene.anims) {
      scene.anims.globalTimeScale = factor;
    }
  },
  { factor: SLOW_MO_FACTOR },
);

The 5 subsystems:

1. Update delta — scene.update(time, delta * factor) slows frame-delta-dependent logic
2. Tweens — scene.tweens.timeScale slows all tween animations
3. Scene timers — scene.time.timeScale slows scene.time.addEvent() timers
4. Physics — scene.physics.world.timeScale slows Arcade/Matter physics (uses inverse: 1/factor)
5. Animations — scene.anims.globalTimeScale slows sprite animation playback

5. Video Finalization

const video = page.video();
await context.close(); // MUST close context to finalize the video file
const videoPath = await video.path();

Full Capture Script Template

import { chromium } from "playwright";
import path from "path";
import fs from "fs";
import { fileURLToPath } from "url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const PROJECT_DIR = path.resolve(__dirname, "..");

// --- Config ---
const args = process.argv.slice(2);
function getArg(name, fallback) {
  const i = args.indexOf(`--${name}`);
  return i !== -1 && args[i + 1] ? args[i + 1] : fallback;
}

const PORT = getArg("port", "3000");
const GAME_URL = `http://localhost:${PORT}/`;
const VIEWPORT = { width: 1080, height: 1920 }; // 9:16 mobile portrait
const SLOW_MO_FACTOR = 0.5;
const DESIRED_GAME_DURATION = parseInt(getArg("duration", "13000"), 10);
const WALL_CLOCK_DURATION = DESIRED_GAME_DURATION / SLOW_MO_FACTOR;
const OUTPUT_DIR = path.resolve(PROJECT_DIR, getArg("output-dir", "output"));
const OUTPUT_FILE = path.join(OUTPUT_DIR, "promo-raw.webm");

// <ADAPT: Generate game-specific input sequence>
function generateInputSequence(totalMs) {
  const sequence = [];
  let elapsed = 0;

  // Pause for entrance animation
  sequence.push({ key: null, holdMs: 0, pauseMs: 1500 });
  elapsed += 1500;

  // <ADAPT: Replace with game-specific keys and timing>
  const keys = ["ArrowLeft", "ArrowRight"];
  let keyIdx = 0;

  while (elapsed < totalMs) {
    const holdMs = 150 + Math.floor(Math.random() * 450);