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

# Experiments Overview

> Add interactive jsPsych experiments to your quests — with multi-experiment support, media uploads, and mobile compatibility.

Experiments are **interactive tasks** — typically built with jsPsych — that participants complete as part of a quest. A quest can hold multiple experiments with defined ordering, and participants can run them on both web and mobile.

## What Is an Experiment?

Each experiment in a quest has:

| Field                  | Required? | Description                                   |
| ---------------------- | --------- | --------------------------------------------- |
| **Name**               | ✅ Yes     | Display name shown on the experiment card     |
| **Description**        | Optional  | Short description shown below the name        |
| **Image URL**          | Optional  | Thumbnail image for the experiment card       |
| **Code**               | ✅ Yes     | HTML/JavaScript code (typically jsPsych)      |
| **Duration (minutes)** | Optional  | Estimated time shown to participants          |
| **Category**           | Optional  | Category tag                                  |
| **Instructions**       | Optional  | HTML instructions shown before the experiment |

## Multi-Experiment Quests

A quest can have **multiple experiments**. When participants view the quest:

* Experiments are displayed as **horizontally scrollable cards** with thumbnail, name, description, and duration
* The active experiment is **highlighted**
* Clicking a card selects that experiment
* Participants can complete experiments in sequence
* Experiments can have **dependencies** — locking them until prerequisites are completed
* **Auto-trigger** can automatically advance to the next experiment after completion

## Data Flow

When a participant completes an experiment:

1. The jsPsych experiment calls `jatos.endStudy(data)` to submit results
2. Data is captured by the NeuroFusion runner
3. Saved locally first (for offline resilience on mobile)
4. Synced to the server and stored in Azure Blob Storage
5. Recorded as an `experiment_data` dataset

## Billing

Each experiment data submission is billed as `quest_experiment` to the quest's organization. See the **[Pricing page](https://usefusion.ai/pricing)** for current costs.

## Backward Compatibility

Older quests with a single `experimentUrl` string (the legacy format) continue to work. The system automatically treats them as a single-experiment quest.

## Explore

<CardGroup cols={2}>
  <Card title="Experiment Editor" icon="code" href="/experiments/experiment-editor">
    Monaco code editor, jsPsych template, and live preview.
  </Card>

  <Card title="Media Uploads" icon="image" href="/experiments/media-uploads">
    Upload images, audio, and video for your experiments.
  </Card>

  <Card title="Ordering & Assignment" icon="list-ol" href="/experiments/ordering-and-assignment">
    Order experiments and use assignment scripts for counterbalancing.
  </Card>

  <Card title="Running on Mobile" icon="mobile" href="/experiments/running-on-mobile">
    Run experiments in the Fusion mobile app.
  </Card>
</CardGroup>