Sure! Here's a simple game implementation that meets your requirements. Just copy and paste the code into a single HTML file and save it. You can then open the file in a web browser to play the game.
To play the game, simply click on the game canvas to shoot bullets and press the "R" key to reload your gun. Your goal is to survive for as long as possible by shooting the incoming zombies. Your health and score will be displayed at the top left corner of the canvas.
Note: This is a basic implementation and can be further expanded and improved according to your specific requirements.