Sure! Here's an example of a simple game about Mario eating mushrooms implemented in a single HTML file:
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🍄
In this game, Mario and mushrooms are represented by emoji/pictograms. Mario is represented by the 🍄 emoji, and the mushrooms are also represented by the 🍄 emoji. When you click/tap on a mushroom, it will be removed from the screen, and a new mushroom will appear in a random position.