Sure, here's an example of a simple Sega-style Batman game implemented as a single HTML file, using JavaScript and enclosed in script tags:
This HTML file sets up a simple Sega-style Batman game where you can choose between 10 characters with Batman in the middle. The game uses a low graphics approach and you can select the characters using arrow keys or "A" and "D" keys. The selected character will be highlighted in red. The initial character is set to Batman, but you can switch between the characters using the arrow keys or "A" and "D" keys.
Note: This is a simplified version and doesn't include actual gameplay or advanced features. It focuses on the character selection part of the game.