Sure, here's a basic game implemented as a single HTML file using JavaScript. This game features building mechanics, RPG elements, zombies, and levels. Please note that this is a simplified version and you can enhance and expand it further to suit your requirements.
In this game, you control the blue player character with the arrow keys on your smartphone. The objective is to avoid the green zombie and survive for as long as possible. If the player collides with the zombie, the game displays a "Game Over" message.
Remember, this is just a basic example, and you can expand upon it by adding building mechanics, RPG elements, levels, and more.