Neuroevolution for Snake

This is a project for a course at KTH Royal Institute of Technology: ID1214 Artificial Intelligence and Applied Methods.

We were able to freely choose a project to implement in the field of AI. We chose to do a neuroevolution project with the classic game Snake.

We implemented the Neural Networks from scratch ourselves, along with a Genetic Algorithm that simulates crossover, mutation, and elitism.

Controls

• M: Menu (Reset / Adjust Settings)
• V: Visualize Mode (Watch the best snake play)
• T: Train Mode (Fast-forward training)

Requirements

The project is designed for Linux. It is possible to get it working for windows but you will need to link SDL2 yourself.

• C++ Compiler: GCC (g++) or Clang with support for C++17 or higher.
• GNU Make: To use the provided makefile.
• SDL2: The core development libraries for Simple DirectMedia Layer.

Installing Dependencies

Ubuntu / Debian

sudo apt-get install libsdl2-dev

Arch Linux:

sudo pacman -S base-devel sdl2

Fedora:

sudo dnf install @development-tools SDL2-devel

Building & Running

make
./build/bin/snake

Highlights

Neural Network

• Developed by us from scratch.
• 11 Inputs (Vision & Orientation)
• 3 Outputs (left, right, forwards)
• RELU, Sigmoid and Tanh activation functions.
• Adjustable hidden nodes.

Inputs

The snake "sees" the world through 11 normalized values (0 or 1): Danger Detection (Relative to Head)

• Danger Left: Is there a wall or tail body part immediately to the left of my head?
• Danger Straight: Is there a wall or tail body part immediately in front of me?
• Danger Right: Is there a wall or tail body part immediately to the right of my head?

Food Direction (Relative to Head)

• Food is Left: Is the food somewhere to the left side of my current path?
• Food is Right: Is the food somewhere to the right side of my current path?
• Food is Straight: Is the food directly ahead of me (in the cone of vision)?
• Food is Behind: Is the food behind me?

Tail Direction (Absolute / Compass)

• Tail is West: Is the tail tip to the left (screen X) of the head?
• Tail is East: Is the tail tip to the right (screen X) of the head?
• Tail is North: Is the tail tip above (screen Y) the head?
• Tail is South: Is the tail tip below (screen Y) the head?

Genetic Algorithm

• Developed by us from scratch
• Elitism: The best snake from the previous generation is copied over unchanged to prevent regression.
• Mutation: Random adjustments to weights to introduce new behaviors.
• Crossover: Combining the "genes" of two parent snakes to create offspring.