Sure, here's a basic implementation of the Snake game in a single HTML file using JavaScript:
This implementation creates a game board using a CSS grid layout. The snake and the food are represented by CSS classes with different background colors. The game logic is implemented in JavaScript, and it includes functions for updating the game state, checking for game over condition, drawing the game board, and handling key events for controlling the snake's direction.
To play the game, you can use the arrow keys on your smartphone to control the snake's movement. The goal is to eat the food and avoid colliding with the snake's body or the game board edges. The game score is displayed, and when the game ends, a message box will appear showing your final score.