in the end part of game the heat is no problem, money isn't a big problem (just
tried to go for a walk into desert valley with exterminator and got 1300
circuits in 7 minutes), price of invisibility source is 600
with >15 s of invisibility you can easily go somewhere, kill some bots, go far
enough to hide, get invisible again, go back etc. (basically the same like
normally, just without bots trying to kill you)

possible solutions
- make some bots ignore invisibility
- make invisibility shorter, more expensive, produce more heat etc.
- using weapon breaks invisibility for a while (bots shooting to place from shot
was fired, moving to that place)
- getting into contact with bot breaks invisibility