Metris is a puzzle game with four modes.
The first mode "Training" is a tutorial with no challenge or goal. It demonstrates that rails need to be connected left to right across the screen.
It can also help you with orienting your finger to correctly hit the tile you are aiming for and it can teach you that tiles only rotate clockwise.
The second mode "Puzzle" one tile drops every time you rotate a piece. You must connect an unbroken line of rail from the left side of the screen to the right. Longer and more complex lines score more points then those tiles used disappear. Once the screen is full you lose.
In the third mode "Survival" tiles continually drop whether or not you take any action. You try to score as many points as you can before the screen fills.
The last mode, "Time Attack", gives the player two randomly selected tunnels to connect before the time runs out. Scores are rewarded for fast completion.
The game also offers score leaderboards, and advertisements and an in-app purchase to turn off the advertising.