After your attempt to destroy the enemy, it's his turn to fight back. The tricky part is that you can't move during his turn. If you got too exposed trying to find the best shooting position, that could come back to byte you in the tail. The easier you shoot at the enemies, the easier they can shoot back. So it's smart to always keep that safe distance as much possible. Use craters in the ground as your cover.
Both WASD and arrow keys model works good, allowing you to move to the left and right and to set gun elevation. To fire a missile you should press the space bar. To fly up you should use 'C' or 'Ctrl' key.Hint: Maybe the most important aspect of the gun in respect to winning is to set the maximum amount of shooting power. Direct hit with 100% power will literally blast your enemy. So always try to get a clean direct shot with the maximum power.