I guess I'll explain a bit more in detail what the 'fluidity' I'm seeing is, and why I'm not sure how to implement it.
Right now the player ship and enemy ships are powered by accelerations. When the player ship gets within some distance of an enemy ship, it reverses acceleration to give the impression of strafing. However, this looks very 'controlled' and after some time, it just looks like the ship is just being repetitive.
The SPAZ main menu features ships that rapidly accelerate and decelerate to the point where it looks like some of them are stopping and then changing direction, in addition to the 'strafing' I have already implemented. This creates a dynamic feel to the main menu where the ships seem to move in very dynamic and fluid motions.
It could just be that I need to increase the rate of acceleration and deceleration of what I already have, but then comes the issue of having an invisible boundary to prevent the player ship from being off-screen for too long.