Sure, here's an example of a simple game called "Walk the Line" implemented as a single HTML file using JavaScript and enclosed in script tags:
Walk the Line
In this game, you control the player's character represented by a black box. The objective is to hide behind the telephone pole, represented by a brown rectangle, to avoid being caught by your girlfriend, represented by a pink rectangle. You can move the player left and right using the arrow keys on a smartphone.
If the player is caught behind the pole, a pop-up alert will appear saying "Game Over! Girlfriend caught you." The player will be reset to the starting position in the middle and can continue playing.
Note: This is a very basic implementation of the game mechanics. You can further enhance it by adding levels, scorekeeping, animations, sound effects, and other features as per your requirements and preferences.