Because you can't control both your jetpack and your gun at the same time, you have to be very careful how you use them. You'll want to get some height before letting go to shoot the enemies.

Remember that you don't need to collect all of the Atomiks to advance in the game. Some of them are too difficult to reach, so if you can't do it, just ignore them.

Another good thing about the Atomiks is that they can act as guides, showing you the way through the level. Just look for them if you ever get lost.

While gun seems like an obvious choice in a lot of situations, try to focus more on your flying skills. If you don't use the gun, you will have a full control over the jetpack and might maneuver easier through the level.

Although there aren't any actual jumping in the game, you can use the gravity and a single burst of your jetpack to reach lower parts of the level, without too much hassle.