> ## Documentation Index
> Fetch the complete documentation index at: https://docs.spire.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# First Based L3 Appchain

> Live demo of the first based L3 appchain demonstrating synchronous composability

## Live Demo

Experience **the first based L3 appchain** in action—a landmark demonstration of synchronous composability between an L3 appchain and its settlement layer (Base).

[**Try the Live Demo →**](https://pylon-demo.base-mainnet.spire.dev/)

## What This Demo Shows

The demo showcases a based L3 appchain **synchronously reading data** from its L2 settlement layer in real-time. While this may seem simple, the implications are significant—it previews a world where millions of appchains operate in sync, all secured by Ethereum's unified network.

### Key Features

* **Synchronous composability** - The appchain reads settlement layer state atomically, without async bridges or oracles
* **Real-time data** - Oracle feed and balances update synchronously from Base
* **Interactive trading** - Buy and sell WETH directly on the appchain using settlement layer data
* **Leaderboard and history** - Track transactions and activity across the network

### What You'll Experience

When you connect your wallet and interact with the demo, you're experiencing:

* **Atomic cross-chain reads** - The appchain queries Base contract state in the same transaction
* **No oracles needed** - Direct access to settlement layer data eliminates oracle risks
* **Seamless UX** - Operations feel like they're happening on a single chain

## How It Works

The demo uses Pylon's synchronous composability infrastructure:

1. **Appchain deployment** - A based L3 appchain settles to Base L2
2. **Cross-chain reads** - When the frontend queries WETH balance or price, it calls contracts that read from Base
3. **Coordinated sequencing** - Pylon's coordinator detects these calls, forwards them to Base, and injects results back
4. **Synchronous execution** - All operations complete atomically in a single transaction

Under the hood, the app uses forwarding proxies that make settlement layer contracts callable as if they were deployed on the appchain itself.

For technical details, see the [simplest-pylon-demo](https://github.com/spire-labs/simplest-pylon-demo) repository.

## Why This Matters

This demo represents a significant step toward a unified Ethereum:

* **Lightweight deployment** - Developers can easily deploy their own L3, inheriting composability and tooling
* **No expensive oracles** - Direct settlement layer access eliminates oracle costs and risks
* **Customizability** - Full control over execution environment while maintaining ecosystem compatibility
* **Scalability + liquidity** - Achieve appchain scalability while accessing underlying L2 liquidity and users

Compared to traditional L3s and appchains, Pylon unlocks synchronous composability without sacrificing the benefits of dedicated execution environments.

## Next Steps

After exploring the demo:

* **[Quickstart](/pylon/quickstart)** - Deploy your own cross-chain application
* **[Build Onchain](/pylon/build-onchain)** - Learn to build similar apps
* **[Core Concepts](/pylon/based-appchains)** - Understand based appchains and synchronous composability

## What's Coming

This demo shows synchronous reads—a foundational capability. Over the coming months, we're releasing:

* Higher levels of synchronous composability
* Synchronous writes (modify settlement layer state from appchain)
* The first production based L3 appchain

Stay tuned for more updates as we continue building toward a unified Ethereum.

***

[**Try the Live Demo →**](https://pylon-demo.base-mainnet.spire.dev/)