Sure, here's an example code that implements a simple game with the specified requirements:
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This code sets up a game where you can control the emoji using the arrow keys on your smartphone. The emoji starts in the middle of the screen and the arrow keys move it left, right, up, or down. Pressing the spacebar transforms the emoji to a dragon, and pressing it again returns it to the emoji state. The game is implemented using HTML, CSS, and JavaScript, all enclosed in a single HTML file.