I have never programmed before. Please create a complete, working Pong game for me using HTML, CSS and JavaScript, so I can play it in a web browser without installing anything.

Include two paddles, one bouncing ball, a computer-controlled opponent, keyboard controls for my paddle, a scoreboard, a Start button and a Restart button. The first player to score five points wins. Show a clear message when the game finishes.

Include Easy, Medium and Hard difficulty levels, with Easy selected by default. On Easy, make the ball slow, give me a larger paddle and make the computer opponent forgiving, so a complete beginner has time to react. Make Medium moderately challenging and Hard faster and more challenging. Limit how much the ball speeds up during a rally so Easy stays easy. Let me choose the difficulty before starting, and show which level is selected.

Give it a clean, colourful JLG Games Academy style. Explain the controls on the page. Save the game as index.html, style.css and game.js in this folder. Please test the game and explain, in simple language, how I open it and what each file does.