Maybe a bit to simple
you'll want to put a simple screen before the loader (the loader itself takes a bit to load and for some reason on my own computer it just shows a white screen for a few seconds. this happens sometimes and you need a pre-loader loader, just some kinda splash screen that most people won't see unless they have slower computers. if you leave it, people may think the flash is broken and vote 0)
Also, i noticed the game doesn't change much as it progresses, you could have different sorts of enemies spawn up in later levels, if it does do this, i apologize, i'm just in a hurry.
also, the difficulty may be ramping up fast enough. after a few minutes of gameplay it's not much harder than it was at the start