Sure! Here's an example of a simple turn-based space battle game implemented as a single HTML file with JavaScript:
In this game, you control a spaceship that battles against an enemy spaceship. The player can level up the spaceship's weapons and engage in turn-based combat. The game will run for 3 rounds, and after that, the spaceship's weapons will be upgraded.
Note: This is a basic implementation to demonstrate the concept. You can enhance and customize it further according to your preferences and game design requirements.