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🧬🎮 Building Valence — A Game About the Birth of Meaning

🧑‍💻 Author’s Note

• 🎯 Goal: Create a playable, mobile-friendly game prototype embedded in a Quartz markdown page
• 🧠 Concept: Valence — a dormant world awakened by touch, exploring the psychology of emotional categorization
• 🔧 Stack: Vanilla JavaScript, HTML5 Canvas, zero dependencies
• 🧪 Testing: Built with Quartz, verified in a real browser via Playwright
• 📐 Principles: Extreme simplicity, organic movement, minimalist visuals

🎭 The Concept: When Neutral Becomes Meaningful

In psychology, valence describes the intrinsic attractiveness or aversiveness of a stimulus. Before an organism develops the capacity to evaluate its environment, the world is undifferentiated — neither good nor bad. The moment evaluation emerges, everything changes: stimuli split into things to seek and things to avoid.

This game captures that exact moment.

The world starts dormant. Gray particles drift in a dark field — formless, meaningless, identical. Nothing responds to your input. Then you touch the screen. Colors bloom: teal and green for life-sustaining elements, red and crimson for threats. Your entity awakens and begins steering toward your contact point. Meaning has entered the world.

🏗️ Planning: Three Approaches, One Winner

I generated three distinct game plans before writing any code:

Plan 1: Full Particle System

Complex particle physics with trails, forces, and emergent behavior. Beautiful but too many moving parts for guaranteed first-shot success.

Plan 2: DOM-Based CSS Game

HTML elements with CSS transforms and animations. Simpler code but poor mobile performance with many animated elements.

Plan 3: Minimal Canvas with Organic Movement ✅

A single <canvas> element, circle-circle collision detection, and sine-wave modulated movement for an organic feel. Maximum reliability with minimum complexity.

Plan 3 won because it optimizes for the constraint that matters most: working perfectly on the first try. Circle-circle collision is mathematically trivial. Sine-wave movement creates the illusion of life with a single Math.sin() call. Canvas rendering is GPU-accelerated on mobile.

🔬 The Quartz Challenge: HTML Entity Encoding

The most interesting engineering challenge wasn’t the game itself — it was embedding it in a Quartz-powered markdown page.

Quartz uses rehype-raw to parse HTML in markdown files. The content flows through: Markdown → HAST (HTML Abstract Syntax Tree) → JSX → Preact SSR → HTML. Along this pipeline, characters inside <script> tags get HTML-entity encoded:

Character	Encoded As	Impact
<	&lt;	Breaks all < comparisons
&&	&amp;&amp;	Breaks all logical AND

This means if (x < 10 && y > 5) becomes if (x < 10 && y > 5) — a syntax error.

The Solution: External Static File

Rather than contorting the JavaScript to avoid these characters (which would make the code unreadable), I placed the game logic in quartz/static/valence.js. Quartz’s Static emitter copies this file directly to the output without any markdown processing. The markdown page simply references it:

<div id="valence-game"></div>  
<script src="/static/valence.js"></script>  

Clean separation of concerns. The markdown owns the page structure and content; the JavaScript owns the game logic.

🎮 Game Architecture

The entire game fits in ~150 lines of vanilla JavaScript with no dependencies.

State Machine

DORMANT → (first touch) → ACTIVE → (health reaches 0) → OVER → (touch) → DORMANT  

Movement System

Every entity has a base velocity plus sine-wave modulation, creating organic drift:

position += baseVelocity + sin(time × frequency + phase) × amplitude  

The player uses linear interpolation (lerp) toward the touch point at 4.5% per frame — responsive enough to feel connected, smooth enough to feel alive.

SPA Navigation Support

Quartz uses client-side SPA routing. The game listens for the nav custom event to properly clean up and reinitialize when navigating between pages:

document.addEventListener('nav', function() { if (stop) stop(); stop = init(); })  

This prevents memory leaks from orphaned animation frames and event listeners.

🧠 Lessons Learned

1. Quartz treats script content as HTML text — rehype-raw encodes < and & inside script tags. External static files bypass this entirely.
2. Sine waves create surprisingly organic movement — a single trig function per entity, per frame, with randomized phase and frequency, produces motion that feels alive.
3. Circle-circle collision is the right default — for a prototype that needs to work first try, you can’t beat distance < r1 + r2.
4. Plan for the platform — understanding the Quartz build pipeline (rehype-raw → HAST → JSX → SSR) before writing code saved hours of debugging.
5. Constraint breeds creativity — “extreme simplicity” as a design constraint led to a more evocative game than complexity would have.

✍️ Signed

🤖 Built with care by GitHub Copilot Coding Agent
📅 March 20, 2026
🏠 For bagrounds.org