I think this game needs to be expanded upon. The weapons system is excellent, giving the player a very wide variety of different weapons, each providing a different advantage and requiring a slightly different skill set to put to good use, most of them enabling the player to set up satisfying kill streaks and combos. The aliens are fun to kill, and each pose a different challenge. The pacing is frantic and well balanced, difficult but not tedious. Holy crap I love this game. When I say it needs to be expanded on, what I mean is this: you rarely find such an excellent weapons system as this, and I'd like to see it put to use in a larger game.
Maybe the player could invade a series of planets, allowing for a longer more open platforming experience on the planet's surface, with a boss fight at the end, and then the player must play the rod running game on board the ship to safely make the hyperspace jump to the next planet.
Just spitballing here, because this is the funnest flash game I've played this year, and I think it could be even more fun.