Great Game. That the shoot convert to money and get harmless after you kill the enemy is a great idea and the key to win the game.
I finished with knight and with magic it is fun and entertaining, too!
The key is to position many lasers exactly where the mother ships are the most concentraed. And some fully upgraded missiles. Dont waste any laser not shooting the mother ships when they stopped moving more or less.
weapon 2/6 was also my last mission.
First build 6-9 misslie launchers and one, two lasers for the first ships. Dont upgrade so you can sell the at initial cost.
Then watch exactly where the mother ships which appear at the and are the most concentrated (1-2 energy lines upwards/downwards from the ship to protect). Exactly there and nowhere else concentrate lasers. Dont upgrade most lasers to pulsers. Maybe only one in the middle to protect the ship against these little enemy ships).
In the middle position fully upgraded missile launchers. 4,5 I think.
The lasers will do the most job. Simple, not upgraded lasers shoot few times but have good power.