This is a basic implementation of "Plants vs. Zombies" game using JavaScript within a single HTML file. The game can be played on a smartphone by touching/clicking on the canvas to create zombies, while moving the player character (green square) using touch/mouse movement. The zombies fall down from the top of the screen and disappear when they reach the bottom.
Note: This code represents a simplified version of the actual "Plants vs. Zombies" game and does not include additional features such as plants, levels, UI elements, etc.