WPF locate discreted points via periodically and set transparency via the alpha,the first parameter

//xaml
<Window x:Class="WpfApp229.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp229"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Canvas x:Name="cvs" />
</Window>


//cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp229
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        List<Point> elpPoints { get; set; }
        int idx = 0;
        int len = 0;
        Ellipse localtedElp { get; set; }
        public MainWindow()
        {
            InitializeComponent();
            this.Loaded += MainWindow_Loaded;

        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            DrawEllipses();
            len = elpPoints.Count;
            localtedElp = new Ellipse();
            localtedElp.Width = 50;
            localtedElp.Height = 50;
            localtedElp.Fill = new SolidColorBrush(Color.FromArgb(128,255,0,0));
            if(!cvs.Children.Contains(localtedElp))
            {
                cvs.Children.Add(localtedElp);
            }
            PeriodicallyLocate();
        }

        private void PeriodicallyLocate()
        {
            Thread.Sleep(1000);
            System.Timers.Timer tmr = new System.Timers.Timer();
            tmr.Elapsed += Tmr_Elapsed;
            tmr.Interval = 1000;
            tmr.Start();
        } 

        private void Tmr_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            if (idx++ < len-1)
            {
                Dispatcher.BeginInvoke(new Action(() =>
                {
                    var x = elpPoints[idx].X;
                    var y = elpPoints[idx].Y;
                    Canvas.SetLeft(localtedElp, x-10);
                    Canvas.SetTop(localtedElp, y-10);
                })); 
            }

        }

        private void DrawEllipses()
        {
            int width = (int)this.ActualWidth - 15;
            int height = (int)this.ActualHeight - 15;
            elpPoints = new List<Point>();
            Random rnd = new Random();
            for (int i = 0; i < 500; i++)
            {
                Ellipse elp = new Ellipse();
                elp.Width = 30;
                elp.Height = 30;
                elp.Fill = new SolidColorBrush(Colors.Blue);
                double x = rnd.Next(0, width);
                double y = rnd.Next(0, height);
                Canvas.SetLeft(elp, x);
                Canvas.SetTop(elp, y);
                cvs.Children.Add(elp);
                elpPoints.Add(new Point(x, y));
            }
        }
    }
}