Sure, here's an example of a simple game implemented as a single HTML file using JavaScript and enclosed in script tags:
Roblox Tycoon
Click the button to earn points!
Score: 0
In this game, you click on the "Button" image to earn points, and the score is displayed below the button. You can further expand the game by adding more features, levels, and logic according to your requirements. This basic game structure will work for a Roblox tycoon-like game on a smartphone.