Only a few very minor issues, not even enough to take it down to 4 stars.
-There's a really big gap between the difficulty of the levels themselves and the bosses, the levels are just a slaughter with the spread gun. (Although.... going through a level and wrecking everything is a nice little power trip lol)
-The 'Just Keep Swimming' achievement isn't matched with the in-game achievement (In-game needs 800 while the NG needs 1000)
-Maybe a few more tracks for the levels and bosses? (The tracks matched the game and I loved them but one or two more couldn't hurt)
Other than that.... it's perfect. No trouble with the controls, no slowdown when the screen is filled and the minigames run as well as the main game.
Both of my thumbs are up for this fine piece of flash.