Sure, here's an example of a simple game written in a single HTML file using JavaScript:
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This game is a simple pictogram matching game where the player needs to click on the pictograms as fast as possible. Each time a pictogram is clicked, the score increases and the pictogram disappears. When all pictograms are clicked, a message will be displayed congratulating the player for completing the game. The game interface is optimized for smartphone operation with clickable pictograms in the form of emojis.