In the level with the blue fire and eyes, if you look closely you can see what I am assuming to be kanji (It is written in blue around the blue fire), but I'm not sure what it says.
I apologize for not combining my last two comments into one: I have a tendency to make a comment and then come up with more content that I should have put in the previous comment, but I have to make a separate comment because most websites will not let you edit a comment.
To find the cost of a tower and all its upgrades from the selling price of that tower, use f(x)=1.25x; meaning that a tower and all its upgrades will sell for 80% of what you paid for a tower and all its upgrades.
To find the cost of something in hard as compared to medium (the prices used in sandbox mode), use: f(x)=x+(x/12.5); then round the number to the nearest multiple of five.
 "Chibi Knight"){kind=icon}
 "Space is Key 2"){kind=icon}
 "This is the Only Level TOO"){kind=icon}
 "Super Karoshi"){kind=icon}
 "Run Raptor Rider"){kind=icon}
 "Bloons TD 5"){kind=icon}
 "Bullet Heaven"){kind=icon}
 "Trollface Launch"){kind=icon}
 "Epic Battle Fantasy 3"){kind=icon}
 "Concerned Joe"){kind=icon}
 "Burrito Bison Revenge"){kind=icon}