using System;

​

namespace App

{

    internal interface IPlayable

    {

        void Play();

        void Stop();

    }

​

    // Define a new interface called IDownloadable

    internal interface IDownloadable

    {

        void Download();

    }

​

    class VlcPlayer : IPlayable

    {

        public void Play()

        {

            Console.WriteLine("Vlc player is playing video.");

        }

​

        public void Stop()

        {

            Console.WriteLine("Vlc player is paused.");

        }

    }

​

    class SpotifyPlayer : IPlayable, IDownloadable

    {

        public void Play()

        {

            Console.WriteLine("Spotify player is playing music.");

        }

​

        public void Stop()

        {

            Console.WriteLine("Spotify player is paused.");

        }

​

        public void Download()

        {

            Console.WriteLine("Spotify player is downloading music.");

        }

    }

​

    class HelloWorld

    {

        // Use a common name, such as value or item, rather than repeating the type name

        public static void TestPlayable(IPlayable item)

        {

            item.Play();

            item.Stop();

        }

​

        public static void TestDownloadable(IDownloadable downloadable)

        {

            downloadable.Download();

        }

​

        public static void Main(string[] args)

        {

            VlcPlayer vlc = new VlcPlayer();

            SpotifyPlayer spotify = new SpotifyPlayer();

            Console.WriteLine("Vlc Player Test!");

            TestPlayable(vlc);

            Console.WriteLine("Spotify Player Test!");

            TestPlayable(spotify);

            TestDownloadable(spotify);

        }

    }

}