// ── Basic class with fields, methods, getter/setter, static ──────────
class Point {
  x = 0;                    // public instance field (per instance)
  y = 0;

  constructor(x, y) {       // runs on `new Point(...)`
    this.x = x; this.y = y;
  }

  length() { return Math.hypot(this.x, this.y); }  // prototype method

  get r() { return this.length(); }                 // getter
  set r(v) {
    const a = Math.atan2(this.y, this.x);
    this.x = v * Math.cos(a); this.y = v * Math.sin(a);
  }

  static origin() { return new Point(0, 0); }       // static method
}

// ── Private fields and methods ───────────────────────────────────────
class Counter {
  #value = 0;                    // private instance field
  static #MAX = 1_000_000;       // private static field

  get value() { return this.#value; }
  #clamp(n) { return Math.min(n, Counter.#MAX); }   // private method

  increment() { this.#value = this.#clamp(this.#value + 1); }

  static from(n) { const c = new Counter(); c.#value = c.#clamp(n); return c; }
}

// ── Inheritance ───────────────────────────────────────────────────────
class Animal {
  constructor(name) { this.name = name; }
  speak() { return `${this.name} makes a noise.`; }
}

class Dog extends Animal {
  constructor(name) { super(name); }                 // must call super() before `this`
  speak() { return `${super.speak()} Woof!`; }       // override + call base
}

// ── Static blocks (run once when class is evaluated) ─────────────────
class Config {
  static base = '/api';
  static #token;

  static {
    this.#token = crypto.randomUUID?.() ?? 'dev-token';
  }

  static authHeader() { return { Authorization: `Bearer ${this.#token}` }; }
}

// ── Computed method names ─────────────────────────────────────────────
class Greeter {
  ['say' + 'Hi']() { return 'hi'; }
  static ['v' + 1] = 2;            // computed static field
}

// ── Abstract-like base ────────────────────────────────────────────────
class Base {
  constructor() {
    if (new.target === Base) throw new TypeError('Abstract');
  }
}

// ── Arrow method keeps `this` bound without .bind() ──────────────────
class Button {
  count = 0;
  handleClick = (e) => { this.count++; };   // bound arrow as field
}