Sure, as a programmer Lego figure, I can help you create a simple game in a single HTML file using JavaScript. Here's an example of a classic "Guess the Number" game implemented as an HTML game:
This game allows the player to input a number between 1 and 100 and then checks if the guess matches the target number. Messages are displayed based on the guess, and once the correct number is guessed, the input field is disabled. You can run this code in a browser to play the game.