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

Parameter	Default	Effect
SLOW_MO_FACTOR	0.5	Game runs at half speed → 50 FPS output
WALL_CLOCK_DURATION	DESIRED_GAME_DURATION / SLOW_MO_FACTOR	Record for 2× to get correct game-time
VIEWPORT	{ width: 1080, height: 1920 }	9:16 mobile portrait (always default unless user specifies otherwise)
DESIRED_GAME_DURATION	13000 (ms)	~13s of game-time → ~6.5s promo clip

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:

Game Type	Input Keys	Pattern
Side dodger	ArrowLeft, ArrowRight	Alternating holds (150-600ms) with variable pauses, occasional double-taps
Platformer / Flappy	Space	Rhythmic taps (80-150ms hold) with variable gaps (200-800ms)
Top-down	WASD / Arrows	Mixed directional holds, figure-eight patterns
Shooter	ArrowLeft/Right + Space	Movement interleaved with rapid fire
Clicker/Tapper	Mouse click / Space	Rapid bursts separated by brief pauses

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 games built with the make-game pipeline 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);
    const pauseMs = 50 + Math.floor(Math.random() * 250);

    // Occasional double-tap for variety
    if (Math.random() < 0.15) {
      sequence.push({ key: keys[keyIdx], holdMs: 100, pauseMs: 60 });
      elapsed += 160;
    }

    sequence.push({ key: keys[keyIdx], holdMs, pauseMs });
    elapsed += holdMs + pauseMs;

    // Alternate direction (with occasional same-direction repeats)
    if (Math.random() < 0.75) keyIdx = 1 - keyIdx;
  }

  return sequence;
}

async function captureGameplay() {
  console.log('Capturing promo video...');
  console.log(`  URL: ${GAME_URL} | Viewport: ${VIEWPORT.width}x${VIEWPORT.height}`);
  console.log(`  Game duration: ${DESIRED_GAME_DURATION}ms | Wall clock: ${WALL_CLOCK_DURATION}ms`);

  fs.mkdirSync(OUTPUT_DIR, { recursive: true });

  const browser = await chromium.launch({ headless: true });
  const context = await browser.newContext({
    viewport: VIEWPORT,
    recordVideo: { dir: OUTPUT_DIR, size: VIEWPORT },
  });

  const page = await context.newPage();
  await page.goto(GAME_URL, { waitUntil: 'networkidle' });

  // Wait for game boot + gameplay active
  await page.waitForFunction(() => window.__GAME__?.isBooted, { timeout: 15000 });
  await page.waitForFunction(() => window.__GAME_STATE__?.started, { timeout: 10000 });
  await page.waitForTimeout(300);
  console.log('  Game active.');

  // <ADAPT: Patch out death — find the actual methods from GameScene.js>
  await page.evaluate(() => {
    const scene = window.__GAME__.scene.getScene('GameScene');
    if (scene) {
      scene.triggerGameOver = () => {};
      scene.onPlayerHit = () => {};
    }
  });
  console.log('  Death patched.');

  // Slow all 5 Phaser time subsystems
  await page.evaluate(({ factor }) => {
    const game = window.__GAME__;
    const scene = game.scene.getScene('GameScene');
    const originalUpdate = scene.update.bind(scene);
    scene.update = function(time, delta) { originalUpdate(time, delta * factor); };
    scene.tweens.timeScale = factor;
    scene.time.timeScale = factor;
    if (scene.physics?.world) scene.physics.world.timeScale = 1 / factor;
    if (scene.anims) scene.anims.globalTimeScale = factor;
  }, { factor: SLOW_MO_FACTOR });
  console.log(`  Slowed to ${SLOW_MO_FACTOR}x.`);

  // Execute input sequence
  const sequence = generateInputSequence(WALL_CLOCK_DURATION);
  console.log(`  Playing ${sequence.length} inputs over ${WALL_CLOCK_DURATION}ms...`);

  for (const seg of sequence) {
    if (!seg.key) { await page.waitForTimeout(seg.pauseMs); continue; }
    await page.keyboard.down(seg.key);
    await page.waitForTimeout(seg.holdMs);
    await page.keyboard.up(seg.key);
    if (seg.pauseMs > 0) await page.waitForTimeout(seg.pauseMs);
  }

  console.log('  Input complete.');

  // Finalize video
  const video = page.video();
  await context.close();
  const videoPath = await video.path();

  if (videoPath !== OUTPUT_FILE) {
    fs.renameSync(videoPath, OUTPUT_FILE);
  }

  await browser.close();
  console.log(`  Raw recording: ${OUTPUT_FILE}`);
  console.log('Done.');
}

captureGameplay().catch(err => { console.error('Capture failed:', err); process.exit(1); });

FFmpeg Conversion

After recording, convert the raw slow-mo WebM to a high-FPS MP4. The convert-highfps.sh script is bundled with this skill at skills/promo-video/scripts/convert-highfps.sh.

# Copy to project (orchestrator does this)
cp <plugin-root>/skills/promo-video/scripts/convert-highfps.sh <project-dir>/scripts/

# Run conversion
bash scripts/convert-highfps.sh output/promo-raw.webm output/promo.mp4 0.5

The script:

• Applies setpts to speed up the video by 1/factor
• Sets output framerate to 25 / factor (= 50 FPS for 0.5× slow-mo)
• Encodes H.264 with crf 23, yuv420p, faststart
• Verifies output duration, frame rate, and file size

Viewport Defaults

Always record in mobile portrait (9:16) unless the user explicitly requests otherwise. Rationale:

• Games are played on phones — promo footage should show the real mobile experience
• 9:16 is native for TikTok, Instagram Reels, YouTube Shorts
• 1080×1920 is the standard resolution

Aspect Ratio	Viewport	Use Case
9:16 (default)	1080 × 1920	Mobile portrait — TikTok, Reels, Shorts, Moltbook
1:1	1080 × 1080	Square — Instagram feed, X posts
16:9	1920 × 1080	Landscape — YouTube, trailers, desktop games

Duration Guidelines

Game Type	Recommended Duration	Why
Arcade / dodger	10-15s	Fast action, multiple dodge cycles
Platformer	15-20s	Show jump timing, level progression
Shooter	12-18s	Show targeting, enemy waves
Puzzle	8-12s	Show one solve sequence

Checklist

Before running the capture:

• Dev server is running and responding
• FFmpeg is installed on the system
• Playwright is installed with Chromium
• Game boots directly into gameplay (no menu blocking)
• Death/failure method identified and patched
• Input keys match the game's actual controls
• Entrance animation pause is included (1-2s)
• Output directory exists

After capture:

• Raw WebM exists in output/
• FFmpeg conversion produces valid MP4
• Duration is ~half the raw recording (speed-up worked)
• Frame rate is 50 FPS
• Video shows gameplay (not a black screen)