Once you get/max the Spread bullet upgrade, the gold you spent on the Magazine upgrade will be useless. Spreading is the way to beat this game/Level 30.
@theelfguy5 If you simply kill yourself, it is only you that failed your boss, but the mission can still be accomplished by somebody else. If you do kill The Worm however, the mission can no longer be completed because The Worm is an important asset. Unless he can get a replacement, the Mission is Failed.
@oyyou That comment is just stupid. If there was such button, then you can't change the direction of Green Arrows. Your arrogance just showcases your stupidity.
I still cannot upgrade the background Sir Billy. Do we have to create a new game and lose our current save? Below the 'Upgrade Background' button, there's the 'Rate: -1' . I think I only upgraded it once from straight line to scribbled line, but it's still stuck at the scribbled background.
The achievement can only be achieved if you obtained at least all the endings, where no one died. Seriously, no one has to die, except for those 2 security guards...but oh well. :)
Aside from BennyGreen's suggestion, you can also squeeze in some Lightning spells in there with the Mana upgrade maxed out. The trap that snares enemies also helps (2 rows of it, 3 rows of barricade, then 3 rows of archers on the end). Lightning is a strong spell which is kinda spammable alongside Cannon. You will run out of mana after awhile, so skip the lightning for some time and use cannon,shotgun, and arrow instead.
 "The Peacekeeper"){kind=icon}
 "simian.interface"){kind=icon}
 "A Small Favor"){kind=icon}
 "Incursion 2: The Artifact"){kind=icon}
 "Innkeeper"){kind=icon}
 "The Trader of Stories"){kind=icon}
 "Tree Of Life"){kind=icon}
 "New Splitter Pals"){kind=icon}
 "Maxwell"){kind=icon}
 "Express Way"){kind=icon}
 "Button Masher Idle"){kind=icon}
 "no-one has to die."){kind=icon}
 "Siege Knight"){kind=icon}
 "Hands of War 3"){kind=icon}