marine09666, it's not that simple. if you don't even know the software needed (adobe flash btw) then you shouldn't start something that complex. there is no real tut (as far as i know) for complete tower defense games, and you'd need a few years of expierence to make anything good. I'm not trying to make you feel bad, i'm just trying to tell you to keep stuff realistic
The fastst way to start out in the world of game development is to: download gamemaker, read tutorials, learn about designing games, design a game, then develop it in gamemaker. If you want to go into browser-based game design, you can try out Flash and decide if you want to spend the money for it.
