From the back of the box:
"Trixo is a brainy and fun 3-in-a-row game in which the playfield is constantly transforming. Players aim to collect the most tiles by outsmarting their opponents and manipulating the playfield to their advantage.
"You will get hooked on Trixo!
Trixo is a version of tic-tac-toe where players aim to collect tiles by placing three of them in a row.
Besides X and O tiles, there are Trixo tiles, which can also be collected, and Slide tiles, which allow users to "slide" a row or a column.
Players may place tiles on top of other tiles as long as they are different and the height is not greater than 3.
The winner of the game is the player that collects the most tiles.