let predator;

​

function setup() {

    createCanvas(800, 600);

​

    // Create a flock of particles (fish)

    for (let i = 0; i < 100; i++) {

        flock.push(new Boid(random(width), random(height)));

    }

​

    // Create a predator particle

    predator = new Predator(width / 2, height / 2);

}

​

function draw() {

    background(220);

​

    // Update and display each flocking particle

    for (let boid of flock) {

        boid.flock(flock, predator); // Apply flocking behaviors

        boid.update();

        boid.display();

    }

​

    // Move and display the predator

    predator.move();

    predator.display();

}

​

// Boid class for flocking particles

class Boid {

    constructor(x, y) {

        this.position = createVector(x, y);

        this.velocity = p5.Vector.random2D();

        this.acceleration = createVector(0, 0);

        this.maxSpeed = 3;

        this.maxForce = 0.1;

        this.r = 5;

    }

​

    applyForce(force) {

        this.acceleration.add(force);

    }

​

    flock(boids, predator) {

        let alignment = this.align(boids);

        let cohesion = this.cohere(boids);

        let separation = this.separate(boids);

        let avoidPredator = this.avoid(predator);

​

        // Add the forces to the acceleration

        alignment.mult(1.0);

        cohesion.mult(1.0);

        separation.mult(1.5);

        avoidPredator.mult(2.0); // Stronger repulsion from predator

​

        this.applyForce(alignment);

        this.applyForce(cohesion);

        this.applyForce(separation);

        this.applyForce(avoidPredator);

    }

​

    update() {

        this.velocity.add(this.acceleration);

        this.velocity.limit(this.maxSpeed);

        this.position.add(this.velocity);

        this.acceleration.mult(0);

    }

​

    display() {

        fill(0, 150, 255);

        stroke(0);

        ellipse(this.position.x, this.position.y, this.r * 2, this.r * 2);

    }

​

    align(boids) {

        let perceptionRadius = 50;

        let steering = createVector();

        let total = 0;

        for (let other of boids) {

            let d = dist(this.position.x, this.position.y, other.position.x, other.position.y);

            if (other != this && d < perceptionRadius) {

                steering.add(other.velocity);

                total++;

            }

        }

        if (total > 0) {

            steering.div(total);

            steering.setMag(this.maxSpeed);

            steering.sub(this.velocity);

            steering.limit(this.maxForce);

        }

        return steering;

    }

​

    cohere(boids) {

        let perceptionRadius = 50;

        let steering = createVector();

        let total = 0;

        for (let other of boids) {

            let d = dist(this.position.x, this.position.y, other.position.x, other.position.y);

            if (other != this && d < perceptionRadius) {

                steering.add(other.position);

                total++;

            }

        }

        if (total > 0) {

            steering.div(total);

            steering.sub(this.position);

            steering.setMag(this.maxSpeed);

            steering.sub(this.velocity);

            steering.limit(this.maxForce);

        }

        return steering;

    }

​

    separate(boids) {

        let perceptionRadius = 25;

        let steering = createVector();

        let total = 0;

        for (let other of boids) {

            let d = dist(this.position.x, this.position.y, other.position.x, other.position.y);

            if (other != this && d < perceptionRadius) {

                let diff = p5.Vector.sub(this.position, other.position);

                diff.div(d * d); // Weight by distance

                steering.add(diff);

                total++;

            }

        }

        if (total > 0) {

            steering.div(total);

            steering.setMag(this.maxSpeed);

            steering.sub(this.velocity);

            steering.limit(this.maxForce);

        }

        return steering;

    }

​

    avoid(predator) {

        let perceptionRadius = 100;

        let steering = createVector();

        let d = dist(this.position.x, this.position.y, predator.position.x, predator.position.y);

        if (d < perceptionRadius) {

            let diff = p5.Vector.sub(this.position, predator.position);

            diff.div(d * d); // Weight by distance

            steering.add(diff);

            steering.setMag(this.maxSpeed);

            steering.sub(this.velocity);

            steering.limit(this.maxForce);

        }

        return steering;

    }

}

​

// Predator class for the large particle that repels the flock

class Predator {

    constructor(x, y) {

        this.position = createVector(x, y);

        this.velocity = createVector(2, 2);

        this.r = 20;

    }

​

    move() {

        this.position.add(this.velocity);

​

        // Bounce off walls

        if (this.position.x > width || this.position.x < 0) {

            this.velocity.x *= -1;

        }

        if (this.position.y > height || this.position.y < 0) {

            this.velocity.y *= -1;

        }

    }

​

    display() {

        fill(255, 0, 0);

        stroke(0);

        ellipse(this.position.x, this.position.y, this.r * 2, this.r * 2);

    }

}

​