Sure, here's a simple game implemented in a single HTML file using JavaScript and enclosed in script tags. It can be played on a smartphone and uses pictograms for visuals:
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When you open this HTML file in a browser and tap on the screen, the night sky will gradually get darker as you tap. Each tap adds a new star emoji to the sky. If you tap five times, a congratulations message will appear. You can modify the game logic, visuals, and other aspects to create a more elaborate game if desired.