Here's a tip: Conveyor belts can cross over roads, so use this once you have more than one expansion to increase efficiency. I was stupidly inefficient until I found this out. Went from $50-70 per tick to $900 per tick. With steel production, using multiple iron smelters, you'll need to have separate conveyor paths for each one to maximize efficiency. To do this properly, you'll need more space than you can have without crossing roads.
Plus, the shots the cannon are firing get bigger and bigger, going from a reasonable size to about 20 of them being the size of the moon. They are bigger than the cannon itself.
And why does gravity just fall off when you defeat the wall? Before you were having so much trouble attacking one enemy, but now you are attacking the moon, when a building a few miles away was difficult, the moon is a cakewalk. Some gravity just said "Screw this, I'm out. Have fun with beating the moon!"
...What does that cannon run on? If it can launch missiles from earth to the moon at such a high speed of both firing and missile velocity, that is one amazing cannon.
 "Factory idle"){kind=icon}
 "Burrito Bison: Launcha Libre"){kind=icon}
 "Trigger Knight"){kind=icon}
 "Pingy the Ping Idle RPG"){kind=icon}
 "Trimps"){kind=icon}
 "Destination Kepler"){kind=icon}
 "Freefall Tournament"){kind=icon}
 "Realm Grinder"){kind=icon}
 "Plumber's Creed"){kind=icon}
 "Learn to Fly Idle"){kind=icon}
 "POTATO POTATO POTATO (etc)"){kind=icon}
 "Achievement Unlocked 3"){kind=icon}
 "Swords and Souls"){kind=icon}
 "Tangerine Tycoon"){kind=icon}
Yeah sorry, it means you mustn't click...