_getFromTo(connected, notConnected) {
        let from = [0, 0], to = [0, 0], d;
        let connectedKeys = Object.keys(connected);
        let notConnectedKeys = Object.keys(notConnected);
        for (let i = 0; i < 5; i++) {
            if (connectedKeys.length < notConnectedKeys.length) {
                let keys = connectedKeys;
                to = connected[keys[RNG.getUniformInt(0, keys.length - 1)]];
                from = this._getClosest(to, notConnected);
            }
            else {
                let keys = notConnectedKeys;
                from = notConnected[keys[RNG.getUniformInt(0, keys.length - 1)]];
                to = this._getClosest(from, connected);
            }
            d = (from[0] - to[0]) * (from[0] - to[0]) + (from[1] - to[1]) * (from[1] - to[1]);
            if (d < 64) {
                break;
            }
        }
        // console.log(">>> connected=" + to + " notConnected=" + from + " dist=" + d);
        return [from, to];
    }
Find random points to connect. Search for the closest point in the larger space.
This is to minimize the length of the passage while maintaining good performance.