A simple HTML5 animation game

Hello, I need someone to build me a simple, one page, 2D animation game using HTML5. The design is as follows: Imagine that, at one end, aliens are running out from their home and using trees & rocks for cover. The player is situated at the other end with a gun. The challenge is to shoot the aliens as they come out. There is only one level but it should get comparatively difficult as the player shoots more aliens. You will draw the background, the obstacles and the aliens. There doesn't need to be a person holding the gun. It can simply be a gun only. This is a simple, quick project and I will expect the winner to finish it within 72 hours. Please if you cannot meet this target, then don't bid. I will select based on price and commitment to deliver on schedule. Happy bidding.