Predator-Prey Simulation — Specification

Overview

A browser-based predator-prey simulation rendered in a single HTML file using JavaScript. The grid displays a canvas with a live population chart alongside it.

Grid

• Default size: 100×100 cells
• Grid size is configurable via a UI control
• Each cell holds at most one entity at a time

Entity Tiers

Time Model

Discrete ticks (turn-based). Each tick, all entities act once in tier order (plants first, then prey, predators, super-predators). Processing order within a tier is randomized each tick to avoid directional bias.

Entity Behaviors

Plants

• Each tick, a plant has a fixed probability of spawning one new plant in a randomly chosen adjacent empty cell (von Neumann or Moore neighbourhood, TBD).
• Plants have no energy; they are destroyed when eaten.
• A dead plant cell has a configurable probability each tick of regenerating into a new plant (default 0 %). This models nutrient cycling or seed banks.

Animals (Prey, Predators, Super-predators)

• Prey eat plants
• Predators eat preys and plants, but plants give less energy than prey.
• Super-predators eat prey and predators (animals only)

Colors: - Preys are red - Predators are blue - Super Predators are yellow

Energy

• Each entity starts with a fixed initial energy.
• Energy decreases by 1 each tick (starvation).
• Eating restores energy: plants give less than animals (see configuration).
• An entity dies when its energy reaches 0.

Movement

• Each tick, an animal scans a configurable sight radius for the nearest food target. Default to the neighbouring cells only.

• If a food target is visible, the animal moves one cell toward it (Manhattan-distance step).

• If no food is visible, the animal performs a random walk (moves to a random adjacent empty cell, or stays put if all neighbours are occupied).

Eating

• After moving, if the animal has landed on a cell containing a food target, it eats it: the food entity is removed and the animal's energy increases.

Reproduction

• If an animal's energy exceeds a reproduction threshold, it spawns one offspring in an adjacent empty cell.
• The parent loses a fixed energy cost on reproduction.
• The offspring starts with half the parent's post-reproduction energy.

Configuration Parameters (with defaults)

UI

• Canvas rendering: each cell is a coloured square (green / red / blue / yellow); empty cells are dark grey.
• Live line chart below (or beside) the canvas showing population counts for each tier over time.
• Layout: simulation canvases (grid + chart) on the left; a right-pane column containing all controls and sliders.
• Buttons: Start / Pause, Step (advance one tick), Reset.
• Sliders (right pane, grouped by theme):

Simulation speed - Ticks per second (1–60, default 10)

Population — initial counts - Grid size (number input, 20–200, default 100) - Initial plant count (0–5000, default 500) - Initial prey count (0–500, default 100) - Initial predator count (0–200, default 30) - Initial super-predator count (0–50, default 5)

Plant dynamics - Plant spread probability (0.001–0.500, default 0.03) - Plant regeneration probability (0–100 %, default 0 %): chance per tick that a dead-plant cell spontaneously regrows into a new plant

Animal energy - Prey initial energy (5–60, default 20) - Predator initial energy (5–80, default 30) - Super-predator initial energy (5–100, default 40) - Energy gained by eating a plant (1–30, default 5) - Energy gained by eating an animal (5–50, default 20)

Reproduction - Reproduction energy threshold (10–100, default 40) - Reproduction energy cost (5–50, default 15)

Behaviour - Animal sight radius (1–15 cells, default 5)

Open Questions

• Neighbourhood type for plant spread and animal movement: von Neumann (4 neighbours) or Moore (8 neighbours)?
• Sight radius: short (3), medium (5), or long (10) cells?
• Idle movement: random walk or stay put when no food is visible?