Predator-Prey Simulation

A particle-based ecosystem simulation built with Python and Pygame, implementing emergent Lotka-Volterra dynamics through simple agent rules.

---

Overview

This simulation models a predator-prey ecosystem where blue prey particles and red predator particles interact in real time. Behaviors like flocking, hunting, fleeing, reproduction, and starvation emerge naturally from local rules — no global coordination needed.

---

Features

• Prey (blue)

  • Flock toward nearby prey
  • Flee from predators within detection radius
  • Seek and eat grass to gain energy and extend lifespan
  • Reproduce when colliding with another prey (if fed)
  • Die of old age or overpopulation

• Predators (red)

  • Hunt prey within detection radius
  • Wander when no prey is nearby
  • Seek mates when fed, to reproduce
  • Starve and die if hunger reaches zero
  • Hunger decreases faster when prey is scarce

• Grass (green)

  • Spawns randomly across the field
  • Consumed by prey on contact
  • Continuously regenerates over time

• Physics

  • Elastic collision resolution between particles
  • Velocity capping and friction damping
  • Wall bouncing

---

Project Structure

.
├── main.py         # Entry point — initializes Pygame, spawns particles, runs the game loop
├── particle.py     # Particle class — movement, forces, collision, drawing
└── universe.py     # Universe class — manages all particles, grass, detection, and reproduction

---

Getting Started

Prerequisites

pip install pygame

Running

python main.py

The simulation window title bar shows live counts:

Prey: 72  Predators: 11

---

Configuration

Key constants can be tweaked at the top of each file:

Parameter	File	Default	Description
WIDTH / HEIGHT	all files	800	Window dimensions
PREY0	main.py	50–100	Initial prey count
PREDATOR0	main.py	10–15	Initial predator count
RADIUS	particle.py	200	Detection/interaction radius
V0	particle.py	2	Max particle speed
FORCE	particle.py	0.15	Steering force magnitude

---

Behavioral Rules Summary

Prey:
  + Eat grass  → +energy, longer lifespan
  + Touch prey (if fed) → spawn new prey
  - Touched by predator → removed
  - Old age / overcrowding → removed

Predator:
  + Eat prey → hunger restored, eaten_prey++
  + Touch predator (both fed) → spawn new predator
  - hunger <= 0 → removed

---

Dependencies

• Python 3.8+
• Pygame 2.x

---