Sure, here's an example of a simple city builder game implemented as a single HTML file using JavaScript. Since it's designed for smartphone operation, it incorporates pictograms for a more visually appealing experience. Remember, this is a basic implementation, and you can expand and customize it further as per your requirements.
City Builder RPG
Click on an action to progress:
In this simple game, you have four possible actions to choose from: Build, Gather, Quest, and Upgrade. By clicking on the corresponding pictogram buttons, you can perform the respective action. The game keeps track of your resources (gold and wood) and quests completed, and provides alerts to inform you of the outcomes. Enjoy playing as a single person and building your city in RPG style!