MMO games have a certain motive of player greed. Everyone wants to be the best, that's why a lot of time the game is played, reads a lot about the game, sometimes even reads the source code. However, everything has its dark side, that is, bugs.
SteemNova is a 2moons engine fork, but with many fixed bugs that were very visible. The problem starts to appear when the bugs are not obvious.
Let's take the example of a trader in the game. A trader is a script that allows us to exchange resources for others - for 4 metals we get 2 crystals or 1 deuterium and so on.
He takes a fee of 750 Dark Matter (premium currency) for this.
So we say that e.g. we want to have 1000 crystal and the game will calculate that it's 2000 metal and if we accept it, an exchange will be made and 750 will be taken from the dark matter account.
But there was a bug that I didn't know about. Let's say we want to have 1000 crystal for 2000 metal, but we don't want to pay 750 dark matter.
It was enough to enter a very large number of deuterium. The engine runs "one at a time", so it checked if we could replace the metal with a crystal and we could.
Then it checked if we could exchange metal for deuterium and it was not possible, not enough metal. So of course he rejected the transaction (for the wrong one), and for the wrong transaction he cannot charge a transaction fee.
So you could exchange at the trader's without paying the dark matter (of course only in the first window).
Unfortunately, nobody wants to report this type of errors, because they allow to achieve a considerable resources benefit. :(