Sure, here's an example of a simple overworld game implemented in a single HTML file using JavaScript. This game allows the player to move a character around a grid-based map using smartphone operations (tapping or swiping) and displays pictograms as representations of the character and obstacles.
This code sets up a canvas element and handles touch or swipe events to move the player character on the map. The game map is defined as a 2D array, where each cell represents a specific type (0 for empty space, 1 for an obstacle, 2 for the player, and 3 for the goal). The player moves on the map by tapping or swiping in the desired direction, and the current state of the game is drawn on the canvas using pictograms.
Please note that this is just a basic implementation to demonstrate the concept of an overworld game. You may need to customize and enhance it further based on your specific requirements and design.