Here is a game implementation using the given code and requirements:
This implementation creates a simple Sea Battle game using HTML canvas and JavaScript. The game canvas is a 500x500 area where ships and missiles are drawn. The ships are represented as rectangles, while missiles are represented as circles. The `drawGame()` function is responsible for updating and drawing the game elements on the canvas. The `startGame()` function starts the game loop by calling `drawGame()` every 100 milliseconds.