unibutton/common/player.js

function Player(you) {
    let pos = { x: Math.random() * 5000 - 50, y: Math.random() * 5000 - 50 };
    let camera = { x: -pos.x, y: -pos.y };
    let vel = { x: 0, y: 0 };

    this.camera = camera;
    this.pos = pos;
    this.vel = vel;
    this.rot = 0;
    this.dir = 1;
    this.ticks = 0;

    this.health = 100;

    this.you = you;
}

Player.prototype.bump = function () {
    let player = this;

    if (player.ticks < 10) {
        player.dir *= -1;
    }

    player.vel.x *= 0.3;
    player.vel.y *= 0.3;

    player.vel.x += Math.sin(player.rot) * 12;
    player.vel.y -= Math.cos(player.rot) * 12;

    player.ticks = 0;
}

Player.prototype.handleTick = function(game) {
    let { player } = game;

    let ent = this;

    ent.pos.x += ent.vel.x;
    ent.pos.y += ent.vel.y;

    ent.vel.x *= 0.9;
    ent.vel.y *= 0.9;

    ent.rot += 0.03 * ent.dir;
    ent.rot = ent.rot % (Math.PI * 10);

    ent.camera.x = -ent.pos.x * 0.1 + ent.camera.x * 0.9;
    ent.camera.y = -ent.pos.y * 0.1 + ent.camera.y * 0.9;

    ent.ticks++;

    let dist = ((ent.pos.x - player.pos.x) ** 2) + ((ent.pos.y - player.pos.y) ** 2);

    let dp = (Math.sin(ent.rot) * (ent.pos.x - player.pos.x))
        - (Math.cos(ent.rot) * (ent.pos.y - player.pos.y));

    dp /= dist;

    dp *= 10;

    if (ent.you) return;

    if (Math.random() < -dp && Math.random() > 3 / (ent.ticks+2)) {
        ent.bump();
    }

    if (Math.sqrt(dist) < 96 / 2) {
        player.health --;
    }
}