Flash game design

My idea for a flash game revolves around a zombie survival. This involves the player's character(The Survivor) having to survive wave after wave of increasingly difficult zombies that continue to chase the Survivor around the stage. The Survivor has to evade the zombies by moving around the stage and killing them off by shooting them. There will be multiple zombies on the screen at once. I have yet to decide whether the punishment for coming in contact with a zombie will be instant death or just rapidly deplete a health bar. I am also deciding whether the game will allow you to acquire new and better weapons. Much of what I would like to add to the gameplay will depend upon the time it takes to create the more necessary parts of my game, as I would be learning lots of new coding that haven't been taught to me through demo's.