As an AI text-based model, I'm unable to create and implement an HTML file directly. However, I can provide you with some guidance on how to create a belly expansion game using JavaScript and HTML. Please follow the steps below:

1. Open any code editor and create a new HTML file (e.g., `belly-expansion.html`).
2. Inside the `` tags of your HTML file, create a container element to display the character's belly and any other game elements you may need. For example:
   


   

     
     

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3. Add CSS styling to position and style the game elements. You can add a separate `<style>` tag within the `` section of your HTML file or use an external CSS file.
4. In the `` section of your HTML file, add a `` tag to enclose your JavaScript code.
5. Inside the `` tags, write the JavaScript code to implement the game logic:
   <br>javascript
   // Get necessary elements from the DOM
   const expandButton = document.getElementById('expand-button');
   const character = document.getElementById('character');
   const belly = document.getElementById('belly');

   // Set initial belly size
   let bellySize = 50; // You can adjust this value based on your game's logic

   // Update the belly size and character image based on the bellySize variable
   function updateBelly() {
     belly.style.width = `${bellySize}%`;
     character.style.width = `${100 - bellySize}%`;

     // Check if the belly has reached maximum size
     if (bellySize >= 100) {
       // Game over logic (you can implement how the game ends here: score, timer, etc.)
       expandButton.disabled = true; // Disable the expand button
       expandButton.innerHTML = 'Game Over'; // Change the button text, add a restart button, show a popup, etc.
     }
   }

   // Event listener for the expand button
   expandButton.addEventListener('click', () => {
     bellySize += 10; // Increase belly size by 10 (adjust as needed)
     updateBelly();
   });

   // Call the updateBelly function initially to display the initial belly size
   updateBelly();
   <br>

6. Save the HTML file and open it in a web browser to play the game.
7. You can add additional game mechanics, animations, score tracking, or any other features as per your requirements.

Remember that this is just a basic example to give you a starting point. You can enhance and modify the game according to your preferences and design.