function connected_lines_get_rnd_params() {
    return {
        start_x: Math.random(),
        start_y: Math.random(),
        offs_x: 0.05,
        offs_y: 0.05,
        num_steps: 5,
        line_distance: 7/500,
    };
}


function connected_lines(params) {
    if(typeof params == 'undefined') {
        var params = connected_lines_get_rnd_params();
    }

    var start = new paper.Point(params.start_x, params.start_y);
    var offs = new paper.Point(params.offs_x, params.offs_y);

    var lines = [];
    for(var i=0; i<2; i++) {
        var x = start.x + i*offs.x;
        var y = start.y + i*offs.y;
        var path = new paper.Path({strokeWidth: 5, strokeColor: 'black'});
        for(var s=0; s<params.num_steps; s++) {
            x = (4*x*(1-x)) % 1;
            y = (x+y) % 1;
            var p = new paper.Point(x, y);
            path.add(p);
        }
        lines.push(path);
    }

    var conlines = new paper.Group();
    for(var i=0; i<params.num_steps-1; i++) {
        // TODO use less variables?
        var o0start = lines[0].getOffsetOf(lines[0].segments[i].point);
        var o0end = lines[0].getOffsetOf(lines[0].segments[i+1].point);
        var o1start = lines[1].getOffsetOf(lines[1].segments[i].point);
        var o1end = lines[1].getOffsetOf(lines[1].segments[i+1].point);

        var num_steps2_0 = (o0end - o0start) / params.line_distance;
        var num_steps2_1 = (o1end - o1start) / params.line_distance;
        var num_steps2 = Math.min(num_steps2_0, num_steps2_1);
        for(var j=0; j<num_steps2; j++) {
            var p0 = lines[0].getPointAt(o0start + (o0end-o0start) * (j/num_steps2));
            var p1 = lines[1].getPointAt(o1start + (o1end-o1start) * (j/num_steps2));
            var path = new paper.Path.Line({
                from: p0, to: p1,
                strokeWidth: 2,
                strokeColor: 'black'
            });
            // TODO param: conn lines min length
            if(path.length < 0.001) {
                path.removeSegments();
                delete path;
            } else {
                conlines.addChild(path);
            }
        }
    }

    lines[1].removeSegments();
    delete lines[1];

    return new paper.Group([lines[0], conlines]);
}