As a programmer, I can create a simple game called "War of Emojis and Letters" that can be played as a finished game using only a single HTML file. The game will involve emoji characters and letters from A to Z, and will be optimized for smartphone operation. Here's an example implementation:
In the above implementation, the game board is displayed as a 5x5 grid of tiles, each containing either a random emoji or a random letter from A to Z. When a tile is clicked, a function `onTileClick` is called, which determines whether the clicked tile contains an emoji or a letter and displays an alert accordingly.
Please note that this is a simple example to illustrate the concept, and you can further enhance the game by adding more features, scoring, timers, levels, etc.