Developer Sandbox

Interactive Playgrounds and Demo Environments

When to Use

Use this skill when you need design and build interactive playgrounds that let developers experience your product without commitment. This skill covers playground architecture, pre-populated examples, embedding strategies, gating decisions, and converting playground users to signups. Trigger phrases: "developer...

Let developers experience your product before they commit. A great playground removes the biggest barrier to adoption: uncertainty about whether your product solves their problem.

Overview

Developer playgrounds serve multiple purposes:

• Evaluation: Let developers test before investing setup time
• Learning: Interactive environment for understanding concepts
• Marketing: Demonstrate capabilities without sales calls
• Support: Reproducible environment for debugging issues

This skill covers designing playgrounds that convert curious visitors into active users.

Before You Start

Review the developer-audience-context skill to understand:

• What do developers want to validate before signing up?
• What's the typical evaluation workflow in your space?
• What competing products offer playgrounds?
• What's the minimum viable experience that demonstrates value?

Your playground should answer the questions developers have when evaluating.

Playground Design Principles

Principle 1: Instant Gratification

Developers should see something meaningful within 10 seconds of landing.

Good: Page loads with a working example already running Bad: Empty editor with "Type your code here" placeholder

<!-- Good: Pre-loaded, running example -->
<div class="playground">
  <div class="editor">
    <pre><code>// Analyze sentiment of this text
const result = await api.analyze("I love this product!");
console.log(result.sentiment); // "positive"</code></pre>
  </div>
  <div class="output">
    <pre>{ "sentiment": "positive", "confidence": 0.94 }</pre>
  </div>
  <button class="run-btn">Run ▶️</button>
</div>

Principle 2: Progressive Complexity

Start simple, let developers go deeper as curiosity grows.

Level 1: One-Click Demo

[Analyze Text] → See result immediately

Level 2: Editable Input

[Edit the text] → [Run] → See result

Level 3: Full API Access

Edit code → Modify parameters → See raw request/response

Level 4: Full Playground

Multiple files → Import SDK → Build mini-app

Principle 3: Real API, Real Results

Never fake the results. Use your actual API with sandbox credentials.

Why real matters:

• Builds trust (not a demo, but actual product)
• Shows real performance characteristics
• Demonstrates actual error handling
• No surprises when they sign up

Principle 4: Zero Friction

No signup required for basic playground. No installation. No configuration.

❌ Bad: "Sign up to try the playground"
❌ Bad: "Install our CLI to continue"
❌ Bad: "Configure your environment..."

✅ Good: Works immediately in browser

Pre-Populated Examples

Example Selection Strategy

Choose examples that:

1. Show core value in 30 seconds
2. Solve real problems developers have
3. Demonstrate differentiation from competitors
4. Scale in complexity from simple to advanced

Example Categories

"Hello World" Example

• Simplest possible use of your API
• Should work with zero modification
• Proves the system is working

// Example: Text Analysis API
const result = await api.analyze("Hello, world!");
// Output: { words: 2, characters: 13 }

"Aha Moment" Example

• Shows unique capability of your product
• Creates the "wow, that was easy" reaction
• This is your most important example

// Example: Shows AI doing something impressive
const result = await api.summarize(longArticle);
// Output: A perfect 3-sentence summary

"Real Use Case" Examples

• Actual scenarios developers encounter
• Shows how to solve specific problems
• Multiple examples for different use cases

// Example 1: E-commerce - Analyze product reviews
// Example 2: Support - Classify incoming tickets
// Example 3: Social - Detect spam comments

"Integration" Examples

• Shows product working with popular tools
• Addresses "will this work with my stack?" concern

// Example: Integration with Express.js
app.post('/analyze', async (req, res) => {
  const result = await api.analyze(req.body.text);
  res.json(result);
});

Example Quality Checklist

• Example runs without modification
• Output is interesting/impressive
• Code follows language best practices
• Comments explain what's happening
• Real-world use case is obvious
• Leads to natural "what else can it do?" curiosity

Sharing and Embedding

Shareable Playground URLs

Enable developers to share their playground state:

https://playground.example.com/?code=BASE64_ENCODED_CODE
https://playground.example.com/share/abc123 (stored state)

Use Cases:

• Sharing code with teammates
• Linking from Stack Overflow answers
• Bug reports with reproduction
• Code snippets in blog posts

Embeddable Playgrounds

Let developers embed playgrounds in their own content:

<!-- Embed in documentation -->
<iframe
  src="https://playground.example.com/embed/quickstart"
  width="100%"
  height="400px"
></iframe>

<!-- Or via script tag -->
<div class="example-playground" data-example="quickstart"></div>
<script src="https://playground.example.com/embed.js"></script>

Embedding Considerations

Size and Performance:

• Lightweight embed script (< 50KB)
• Lazy-load playground until visible
• Responsive width, configurable height

Customization:

• Theme options (light/dark, match host site)
• Show/hide specific UI elements
• Read-only vs. editable modes

Attribution:

• Subtle branding that links back
• "Powered by [Product]" footer
• "Edit in full playground" link

Gating vs. Ungating

When to Keep Ungated

Ungated (no signup required) when:

• Developers are evaluating whether to adopt
• Example demonstrates core product value
• Rate limits can prevent abuse
• Goal is top-of-funnel awareness

When to Gate

Gated (require signup) when:

• Using production API resources
• Accessing personal/saved playgrounds
• Advanced features that require account
• Generating API keys for external use

Progressive Gating Strategy

┌─────────────────────────────────────────────────────────┐
│ UNGATED                                                  │
│ • Run pre-built examples                                │
│ • Edit and re-run examples                              │
│ • Share playground URLs                                 │
├─────────────────────────────────────────────────────────┤
│ FREE SIGNUP                                             │
│ • Save playgrounds                                      │
│ • Get API key for external use                         │
│ • Access more examples                                  │
│ • Higher rate limits                                    │
├─────────────────────────────────────────────────────────┤
│ PAID                                                    │
│ • Production API access                                 │
│ • Team features                                         │
│ • Premium models/features                               │
└─────────────────────────────────────────────────────────┘

Gating UX

When you do gate, minimize friction:

<!-- Good: Non-blocking gate -->
<div class="save-prompt">
  <p>Want to save this playground?</p>
  <button free account</button>
  <button without saving</button>
</div>

<!-- Bad: Blocking gate -->
<div class="modal">
  <p>Sign up to continue using the playground</p>
  <form><!-- required fields --></form>
</div>

Playground to Signup Conversion

The Conversion Funnel

Playground Visit
      ↓
Runs First Example (Time to first interaction)
      ↓
Modifies Example (Engagement)
      ↓
Explores More Examples (Interest)
      ↓
Hits Limitation (Trigger)
      ↓
Signs Up (Conversion)

Designing Conversion Triggers

Natural limitations that encourage signup:

// Rate limit message
"You've used 10/10 free playground requests today.
 Sign up for 1,000 free requests/month."

// Feature tease
"This example uses our Pro model.
 Sign up to try it free."

// Save prompt
"Your playground session will expire in 30 minutes.
 Create an account to save your work."

Avoid artificial friction:

// Bad: Arbitrary block
"Sign up to run more than 3 examples"

// Bad: Feature that should be free
"Sign up to see request/response details"

Conversion Best Practices

Clear value proposition:

┌─────────────────────────────────────────┐
│ Create a free account                   │
│                                         │
│ ✓ Get your own API key                 │
│ ✓ Save and share playgrounds           │
│ ✓ 1,000 free API calls/month           │
│                                         │
│ [Sign up with GitHub]                   │
│ [Sign up with Google]                   │
│ [Sign up with email]                    │
└─────────────────────────────────────────┘

Preserve context:

• After signup, return to the same playground state
• Pre-populate API key in their code
• Show "Next steps" relevant to what they were doing

Measure the funnel:

analytics.track('playground_visit');
analytics.track('playground_first_run');
analytics.track('playground_code_edit');
analytics.track('playground_signup_prompt_shown');
analytics.track('playground_signup_started');
analytics.track('playground_signup_completed');

Playground Architecture

Client-Side Playgrounds

Best for:

• JavaScript/TypeScript SDKs
• Browser-based APIs
• When latency matters

Architecture:

┌──────────────────────────────────────────┐
│ Browser                                  │
│  ┌─────────────┐    ┌────────────────┐ │
│  │ Monaco      │    │ Preview/Output │ │
│  │ Editor      │ →  │ Iframe        │ │
│  └─────────────┘    └────────────────┘ │
│         ↓                    ↓          │
│  Bundler (esbuild-wasm) → Execute       │
│                              ↓          │
│                        Your API         │
└──────────────────────────────────────────┘

Server-Side Playgrounds

Best for:

• Python, Go, Ruby, etc.
• When isolation is critical
• Complex dependencies

Architecture:

┌────────────────────────────────────────────────┐
│ Browser                                        │
│  ┌─────────────┐    ┌────────────────────┐   │
│  │ Editor      │    │ Output             │   │
│  └─────────────┘    └────────────────────┘   │
│         ↓                    ↑                │
└─────────│────────────────────│────────────────┘
          │                    │
          ↓                    │
   ┌──────────────────────────────────────┐
   │ Backend                              │
   │  ┌────────────┐    ┌─────────────┐ │
   │  │ Code       │ →  │ Sandbox     │ │
   │  │ Receiver   │    │ Container   │ │
   │  └────────────┘    └─────────────┘ │
   └──────────────────────────────────────┘

Security Considerations

Sandbox isolation:

• Execute user code in containers
• Limit CPU, memory, network
• No filesystem access to host
• Kill runaway processes

API protection:

• Rate limiting per IP/session
• Sandbox-only API credentials
• Monitor for abuse patterns

Content safety:

• Scan generated content
• Block malicious outputs
• Log for audit

Playground UX Components

Essential UI Elements

┌─────────────────────────────────────────────────────────────┐
│ [Examples ▼] [Docs] [Share] [Sign Up]                       │
├───────────────────────────────┬─────────────────────────────┤
│                               │                             │
│  // Your code here            │  Output                     │
│  const result = await         │  {                         │
│    api.analyze("Hello");      │    "sentiment": "neutral"  │
│                               │  }                         │
│                               │                             │
│                               │                             │
├───────────────────────────────┴─────────────────────────────┤
│ [▶ Run]  [Reset]  [Copy Code]  [Copy as cURL]              │
└─────────────────────────────────────────────────────────────┘

Editor Features

• Syntax highlighting
• Autocomplete for SDK methods
• Error highlighting
• Line numbers
• Multiple file support (advanced)

Output Features

• Formatted JSON
• Collapsible nested objects
• Copy output button
• Request/response toggle
• Timing information

Tools

Code Editors

• Monaco Editor: VS Code's editor (feature-rich)
• CodeMirror: Lightweight, extensible
• Ace Editor: Long-standing, battle-tested

Sandboxing

• Firecracker: Lightweight VMs
• gVisor: Container sandboxing
• WebContainers: Browser-based Node.js

Playground Platforms

• CodeSandbox: Full development environments
• StackBlitz: WebContainer-based
• Replit: Multi-language support
• Custom: Build your own for control

Embedding

• iframes: Simple but limited
• Web Components: Better isolation
• Script embeds: Most flexible

Related Skills

• api-onboarding: Playground as onboarding tool
• docs-as-marketing: Interactive examples in documentation
• sdk-dx: SDK design that works in playground context
• developer-metrics: Measuring playground effectiveness
• developer-audience-context: Understanding what to demo

Limitations

• Use this skill only when the task clearly matches its upstream source and local project context.
• Verify commands, generated code, dependencies, credentials, and external service behavior before applying changes.
• Do not treat examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions.