funny game. Some solution:
1. Re-launching starts before killing zone mini boses helps with harvesting all those needed materials, which i find rly helpfull later in the game.
2. Buy those healing machines, at later stages i couldnt find any at shop, and they r rly usefull
3. Dont put all missles next to each other as they will fire at once at one target ( which is a huge waste)
4. Struggling last wave ? U can use a trick - move your ship to the one side of map so that not every enemy will fight u. Bit lame, but this is an easiest way to finish the game.