Since v1.2, there are missiles, which can be bought on the trading station. Double-Click the right mouse button to launch them. They will automatically aim at your enemy and make double damage!
And now in v1.3 there are three levels of difficulty for the Zark-Attack Mission and also a functionally Reset-Button, when you're ship gets destroyed (In v1.1 & v1.2 it doesn't work, now it works again^^).
In v1.4 there is a new mission (called Zark-Destroyer), in which you must eliminate a big destroyer-ship of the Zark.
And in v1.5 there are now two levels of difficulty for the Zark-Destroyer Mission and marine-ships now also attack near enemys.
In v1.6 there is a new mission (called Battle), which creates a battle between Marines and Zark, and you are right in the middle of it!