Sure, here's a sample implementation of a space game using JavaScript, enclosed in script tags within a single HTML file:
This simple space game allows you to control a green rectangular starship using the left and right arrow keys on your smartphone. The objective is to avoid colliding with enemy red starships that move downward from random positions on the screen.
Note: For a more complex game with PvP and battle royals modes, additional logic and functionality would need to be implemented, including multiplayer support.