let particles = [];

function setup() {
    createCanvas(600, 600);
    angleMode(DEGREES);
    frameRate(60);
    noStroke();
    noCursor();
}

function draw() {
    torch();
}

/**
 * 火把
 */
function torch() {
    background(0);
    const x = mouseIsPressed ? mouseX : 300;
    const y = mouseIsPressed ? mouseY : 500;
    // 添加新粒子
    for (let i = 0; i < 5; i++) {
        const p = new Particle(x, y);
        p.velocity.x = random(-1, 1) * 30;
        p.velocity.y = random(-5, -1) * 50;
        particles.push(p);
    }
    // 绘制火把
    fill("lightgray");
    rect(x - 5, y - 10, 10, 80);
    fill("gray");
    rect(x - 7, y - 10, 14, 20);
    // 更新并绘制所有粒子
    push();
    for (let i = particles.length - 1; i >= 0; i--) {
        const p = particles[i];
        p.applyForce(createVector(0, -100));
        p.update();
        if (p.finished) {
            particles.splice(i, 1);
        } else {
            const alpha = map(p.duration, 0, p.life, 255, 0);
            const size = map(p.duration, 0, p.life, 8, 32);
            fill(255, alpha);
            circle(p.position.x, p.position.y, size);
        }
    }
    pop();
}