Inversion:

Inversion is a mechanic in Frenopolis that is based on the fact that a card's stat can be denoted by its rotational position.

An upright card has 4 stat (like most cards), and you can rotate it 90 degrees to the right each time it is reduced by 1 stat (tapping), reaching 0 when it returns to the upright position (and sent to the Archive (graveyard)).

With Inversion, you simply rotate the card 180 degrees. So:
1 -> 3
2 -> 4
3 -> 1
4 -> 2

Inversion as a mechanic applies to all cards a specific Type (both yours and the other player's). It is also a very cheap mechanic in terms of effect to card cost. There are lots of advantageous things you can do with the Inversion mechanic.