How to Make Karaoke Effect For text

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace KaraokeEditor
{
    public class KaraokeDrawer
    {
        PictureBox _pBox;
        public KaraokeDrawer(PictureBox pBox)
        {
            _pBox = pBox;
            _pBox.Paint += pictureBox1_Paint;
            _timer.Tick += Timer_Tick;
            _timer.Start();
        }

        Timer _timer = new Timer() {Enabled = true, Interval = 50};
        
        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            string text = "Hello World!";
            var path = new GraphicsPath();
            path.AddString(text, new FontFamily("Arial"), (int)FontStyle.Regular, 50, new Point(10, 10), StringFormat.GenericDefault);
            e.Graphics.FillPath(new SolidBrush(Color.White), path);

            Region r = new Region(path);
            RectangleF rect = r.GetBounds(e.Graphics);
            RectangleF intersectRect = new RectangleF(rect.X, rect.Y, rect.Width * _percent / 100, rect.Height);
            r.Intersect(intersectRect);
            e.Graphics.FillRegion(Brushes.Red, r);

            e.Graphics.DrawPath(new Pen(Color.Blue), path);
        }
        

        int _percent = 0;
        private void Timer_Tick(object sender, EventArgs e)
        {
            ++_percent;
            _pBox.Invalidate();
            if (_percent >= 100)
            {
                _timer.Stop();
            }

        }
    }
}