HackAtari

HackAtari is an object-centric extension of the Atari Learning Environment (ALE), built on top of OCAtari. It enables custom environment modifications and dynamic reward functions for Atari games in research and experimentation.

OCAtari provides object-based observations for Atari 2600 games, supporting research in interpretable RL, object-centric RL, and environment hacking.

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Features

• Plug-and-play Atari environments with OpenAI Gym interface.
• Object-centric observations (RAM, pixel, or object states).
• Easy-to-use modification system: change rules, visuals, or add obstacles per game.
• Custom reward function injection (Python scripts, at runtime).
• Dopamine-style frame pooling for observation stability.
• Fully human-playable: interactive play mode (keyboard controls via Pygame).
• Game mode and difficulty selection (where supported by ALE).

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Installation

1. Install OCAtari:

   • Follow instructions in OCAtari repository, or install via pip:

     pip install ocatari

2. Install HackAtari:

   • Recommended: install from PyPI:

     pip install hackatari

   • Or, for development:

     git clone https://github.com/k4ntz/HackAtari
     cd HackAtari
     pip install -e .

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Usage

You can use HackAtari environments just like standard OpenAI Gym environments. The included run.py demonstrates launching both standard and modified games, with options for human or random agent play.

Example usage:

# Start normal Freeway (random agent)
python run.py -g Freeway

# Human mode, normal Freeway
python run.py -g Freeway -hu

# Cars of color Black
python run.py -g Freeway -m all_black_cars

# Freeway with stopping mode #3 (static cars)
python run.py -g Freeway -m stop_all_cars

Evaluating Agents with HackAtari Modifications

HackAtari makes it easy to evaluate RL agents not only on standard Atari games, but also on custom or challenging modified environments. This enables robust evaluation of generalization, interpretability, and adaptability in RL research.

Steps to Evaluate Agents using the eval script

0. Install the needed additional packages

pip install torch
pip install stable_baselines3
pip install rliable

1. Choose Your Modification(s)
   See modification_list.md or print them in code:

from hackatari.core import HackAtari
env = HackAtari('Pong')
print(env.available_modifications)

2. Use the eval script

# Start with the baseline performance 
python eval.py -g Freeway -a path_to_model

# Evaluate the same model on a modified version of the game
python eval.py -g Freeway -a path_to_model -m all_black_cars

# Save results in a json file
python eval.py -g Freeway -a path_to_model -m all_black_cars -out results.json

For more parameters, check the eval script.

Game Modifications

• See: modification_list.md or the online docs.
• In code: Use env.available_modifications to print all modifications and their documentation for a given game.

Example

from hackatari.core import HackAtari
env = HackAtari('Freeway')
print(env.available_modifications)

Human Play Mode

Enable human-interactive play (keyboard) with the -hu flag in run.py, or directly instantiate hackatari.core.HumanPlayable in your code.

Keyboard controls:

• P: Pause/Resume
• Q: Quit
• R: Reset
• Arrow keys / action keys: Move or interact (varies per game)

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Custom Reward Functions

Override the environment's reward signal by providing your own reward function script (see examples/ for a template). Pass the path via -r in run.py or as the rewardfunc_path argument:

env = HackAtari('Pong', rewardfunc_path='path_to_my_custom_reward.py')

The reward function should be a Python function:

def reward_function(env) -> float:
    # Your custom reward logic here
    return 0.0

Documentation & Further Resources

• Documentation
• List of modifications
• OCAtari documentation

For in-depth API and modding reference, see the above links.

Citation

If you use HackAtari in academic work, please cite the corresponding paper:

TBH

License

HackAtari is open source under the MIT License (see LICENSE).