How can I make a Winform transparent but not click-trough?

Question

I am attempting to make a Winform application to draw on my screen. My objective is to launch the application, choose a pen and color (which I have not yet implemented), and subsequently draw on my screen. However, I am encountering an issue where, upon setting the form to be transparent, any attempts to draw on the form I just click on the application or desktop located behind it. This is what i have now:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace screendrawer1
{
    public partial class Form1 : Form
    {
        // Define a region for the transparent area
        private Region transparentRegion; private Color currentLineColor = Color.Blue;
        private float currentLineWidth = 2.0f;

        public Form1()
        {
            InitializeComponent();

            // Set the form's initial properties
            this.FormBorderStyle = FormBorderStyle.None;
            this.WindowState = FormWindowState.Maximized;
            this.TopMost = true;
            this.ShowInTaskbar = false;

            // Set the form's opacity to a low value
            this.Opacity = 0.5;

            // Create a new region to represent the transparent area
            transparentRegion = new Region(this.ClientRectangle);

            // Subtract the button's region from the transparent area
            Rectangle buttonRect = guna2ControlBox1.Bounds;
            buttonRect.Offset(guna2ControlBox1.Location);
            transparentRegion.Exclude(buttonRect);

            // Bind the Form1_MouseMove method to the MouseMove event
            this.MouseMove += new MouseEventHandler(Form1_MouseMove);
        }

        private Point? previousPoint = null;
        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                using (Graphics g = this.CreateGraphics())
                {
                    Pen pen = new Pen(Color.Blue, 2); // Set the pen color and width
                    Point currentPoint = e.Location;

                    if (previousPoint != null)
                    {
                        g.DrawLine(pen, previousPoint.Value, currentPoint);
                    }

                    previousPoint = currentPoint;
                }
            }
            else
            {
                previousPoint = null;
            }
        }

        private void guna2ControlBox1_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }

}

I tried:

SetStyle(ControlStyles.SupportsTransparentBackColor, true);
this.BackColor = Color.Transparent;

Which was not helpful because then I couldn't draw on the App. I just clicked trough it.