As an AI language model, I can provide you with a simple example of a combat game implemented as a single HTML file, enclosed in script tags and using JavaScript. However, please note that this will provide a basic structure to get you started, and the game will not have advanced graphics or extensive gameplay. Here's the code:
This game sets up a canvas where two players (represented by colored rectangles) can move up and down using the arrow keys and 'W'/'S' keys. It tracks the key presses to move the players and redraws the canvas on each frame to animate the game.
Please note that this is a very basic implementation example, and for more advanced graphics and gameplay, you would need to use additional libraries or frameworks.