Sure, here's an example of a simple game implemented as a single HTML file, enclosed in script tags, and using JavaScript. This game assumes smartphone operation and uses pictograms for visual representation.
Pictogram Game
Tap the correct pictogram as fast as you can!
Score: 0
In this game, a random pictogram is displayed every 2 seconds and the player needs to tap on the correct pictogram as fast as possible. The score is incremented for each correct tap and displayed on the screen. The game continues indefinitely until the player taps on the wrong pictogram.