Sure, here's a simple implementation of the game you described as a single HTML file:
Giant Slime Boss Fight
To play the game:
1. Open a text editor and copy the above code into a new blank file.
2. Save the file with a `.html` extension (e.g., `slime_game.html`).
3. Open the saved HTML file in a web browser (preferably on a smartphone).
4. Use the arrow keys to move the orange diamond character.
5. Press the Spacebar to launch orange balls towards the giant white slime boss.
6. Hit the boss with the balls to decrease its health. It has a total of 5 health points.
7. Defeat the boss by reducing its health to 0.
Good luck and have fun playing the game!