[рони]

Rise,

<canvas width="400" height="200" style="outline:1px solid black;cursor:none;"></canvas>
<script>
"use strict"
class Point {
    constructor(x, y, radius) {
        this.x = x;
        this.y = y;
        this.radius = radius;
        this.color = "#0000FF";
    }
    render(game) {
        game.ctx2d.beginPath();
        game.ctx2d.fillStyle = this.color;
        game.ctx2d.arc(this.x, this.y, this.radius, 0, 7);
        game.ctx2d.fill();
    }
}
class Cursor extends Point {
    constructor(x, y, radius, length, filter) {
        super(x, y, radius);
        this.length = length;
        this.filter = filter;
        this.color = "#" + ("000000" + (Math.random() * 0xffffff | 0).toString(16)).slice(-6);
        this.points = new Set();
    }
    search(points) {
        this.points.clear();
        for (let point of points) {
            point.color = "#0000FF";
            if (this.filter(this, point)) {
                point.color = "#7FFF00";
                this.points.add(point);
            }
        }

    }
    render(game) {
        this.search(game.points);
        game.ctx2d.beginPath();
        game.ctx2d.strokeStyle = this.color;
        for (let point of this.points) {
            game.ctx2d.moveTo(this.x, this.y);
            game.ctx2d.lineTo(point.x, point.y);
        }
        game.ctx2d.closePath();
        game.ctx2d.stroke();
        super.render(game);
    }
}
class Game {
    constructor(canvas, cursor, points) {
        this.ctx2d = canvas.getContext('2d');
        this.cursor = cursor;
        this.points = new Set(points);
        this.render();
        canvas.onmousemove = (e) => {
            this.cursor.x = e.offsetX;
            this.cursor.y = e.offsetY;
            this.render();
        };
    }
    render() {
        this.ctx2d.clearRect(0, 0, 400, 200);
        for (let point of this.points)
            point.render(this);
        this.cursor.render(this);
    }
}
const theGame = new Game(
    document.querySelector('canvas'),
    new Cursor(200, 100, 2, 50, (A, B) => B.x > A.x - A.length && B.x < A.x + A.length && B.y > A.y - A.length && B.y < A.y + A.length),
    new Array(10 * 20).fill(0).map((v, i) => new Point(20 * (i % 20) + 10, 20 * (i / 20 | 0) + 10, 2))
);
</script>