text: export default class Group {
  	constructor() {
  		this.items = [];
  	}
  	update() {
  		for(const item of this.items) {
  			item.update();
  		}
  	}
  	render(g) {
  		for(const item of this.items) {
  			item.render(g);
  		}
  	}
  	causeEvent(type, events) {
  		for(const item of this.items) {
  			item.causeEvent(type, events);
  		}
  	}
  	add(item) {
  		this.items.push(item);
  	}
  	remove(item) {
  		const i = this.items.findIndex(n => n === item);
  		if(i !== -1) {
  			this.items.splice(i, 1);
  		}
  	}
  	[Symbol.iterator]() {
  		return this.items.values();
  	}
  }