Sure! Here's an example of a simple 300 Spartan-themed fighting game implemented as a single HTML file using JavaScript:
This game sets up a simple game area with a player (red square) and an enemy (blue square). The player can move left and right using the "A" and "D" keys, respectively. Pressing the "W" key triggers an attack, turning the enemy green temporarily if the attack is successful. Feel free to modify and enhance it further to make it a more complete game.