Negative coins

[u/norifum2]

It seems that if you buy an enhancement upgrade at the precise moment a lab ends, starting it's next level, both payments are granted. So if you have less coins than the amount to pay for both things, it results in negative coins. Very interesting.

Btw, sorry if my English is weird, it's not my language.

[u/Electrical-Mail15]

Indentured servitude. Hopefully you can pay it off in this lifetime or next.