One4

Is a 3D puzzle game where you compete against Artificial Intelligence or your Steam mate in a formation of cubes made in glass.
Your aim is to fill four cubes with your characters in a row.

There are three game modes:

Basic - a game where you put characters in their respectable places
Drop - you have gravity, and you drop the character into the set of cubes. After dropping, you need to spin a slice of the cube. Characters fall down as gravity hits like a hammer.
Rotate - similar to drop, but you don't have the gravity

And three difficulty levels:

Easy
Medium
Hard

Difficulty levels only apply to single player games

Two player game

To play the two player game, you need to make friends of other Steam players first.
Do the following:

If you know a friend, who plays on Steam, ask him/her to be your friend
Launch One4, and select 2 player game
Select your friends name from the drop down
If you have not chatted with your friend, you can try to invite by pressing the button underneath the dropdown
You may also click to open the chat and decide which game you wish to play
Once both of you are in the game, you can play together