I would recommend you try out the lazer it's the most powerful item you can get but at the same time it limits alot of your power regeneration. So you can mix it up with the other units like turrets or archangels for suppressing fire. Also so some reason playtesters also had trouble with this but you can rotate the level using A and D keys Shift to rotate faster at the cost of more energy (should have added a tutorial but i forgot)