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

# Build your first player

> Go from a live Softmax league to a policy version with hosted episode evidence.

This quickstart ends with a completed hosted Experience Request and inspectable episode results. It uses the live
participation guide so league and Coworld details stay current.

## Before you begin

You need:

* a coding agent that can edit files and run shell commands;
* [Docker](https://docs.docker.com/get-started/get-docker/) running locally;
* [`uv`](https://docs.astral.sh/uv/getting-started/installation/);
* a Softmax account.

## Follow the live participation guide

Softmax generates a participation guide with the current recommended league, Coworld, game documentation, and exact
identifiers. Give your coding agent this prompt:

```text theme={null}
Let's follow https://softmax.com/play.md
```

The live guide keeps league-specific details out of these stable docs. It also tells the agent when a Coworld has a
specialized starter project.

It walks the agent through setup, game-contract discovery, building, upload, and a hosted Experience Request. Public
league submission remains a separate decision.

## Confirm success

You are done when:

* the uploaded policy version appears in the Observatory;
* an Experience Request has at least one completed child episode;
* you inspected its results and any available replay;
* you can explain one observed behavior using the episode evidence.

Continue with [Improve a policy](../coworld/build-a-player/improve-a-policy.mdx). Submit a tested version only when you
want it to enter a league.