Jump Game

A 2D browser-based platform jumping game built for the David Levari Lab, Department of Cognitive and Psychological Sciences, Brown University. Players hold and release to charge a jump and land a character on platforms across 30 trials. Timing data for each trial is automatically saved to a MongoDB database for research analysis.

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Features

• 30-trial experiment split into three difficulty phases
• Charge-based jump mechanic — hold to build power, release to launch
• Squash-and-stretch animations with spring physics on landing
• Automatic data collection — per-trial timestamps, landing coordinates, and outcomes saved to MongoDB
• Replay viewer — watch any past session played back at 0.5×, 1×, 2×, or 3× speed with live stats
• Participant ID entry before each session for data labeling
• Pause / Restart controls during gameplay
• Touch support — works on touchscreens as well as mouse/trackpad

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Difficulty Phases

Phase	Trials	Platform Width	Target Movement
Easy	1–10	120–140 px	Static
Hard	11–20	50–80 px	Static
Moving	21–30	50–80 px	Oscillates vertically

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Key Functions

Game (jump1.html) Replay Viewer (replay.html) Server (server.js)

How to Play

Setup

1. Install dependencies

   npm install

2. Configure environment — create a .env file in the project root:

   MONGO_URI=mongodb+srv://<user>:<password>@<cluster>.mongodb.net/<dbname>
   PORT=3000
   ALLOWED_ORIGIN=http://localhost:3000
   

3. Start the server

   npm start

   The server starts at http://localhost:3000.

4. Open the game in your browser:

   http://localhost:3000/jump1.html
   

Playing

1. Enter a Participant ID (e.g. P042) and click Start.
2. Hold the mouse button (or press and hold on a touchscreen) to charge the jump — the character squashes as power builds.
3. Release to launch. The jump angle is fixed at ~60° upward-right; power depends on how long you held.
4. Land the character on top of the target platform to score a success. Missing the platform (falling off-screen) counts as a failure.
5. Repeat for all 30 trials. After the final trial the session is automatically saved and a session ID is shown.

Controls during a session:

• Pause / Resume — temporarily freeze the game mid-trial
• Restart — discard the current session and return to the ID entry screen

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Replay

1. Open the replay viewer at:

   http://localhost:3000/replay.html
   

2. Optionally type a Participant ID and click Search to filter sessions, or click Show All.
3. Select a session from the dropdown and click Load & Watch.
4. Use the Speed slider to set playback speed (0.5×, 1×, 2×, 3×).
5. Click Play to start the replay. Use Pause and Restart to control playback.

The replay panel also shows a summary of the session: number of successes, failures, average reaction time (landing → press), and average charge time (press → release).

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Tech Stack

• Frontend — Vanilla HTML5 Canvas, JavaScript (no framework)
• Backend — Node.js, Express
• Database — MongoDB via Mongoose
• Dev server — Nodemon (npm run dev)