Decoder is a game in Arena 39 on The 39 Clues Website. It is the Lucian Challenge in Mission 0.
However it is currently getting fixed.
Goal[]
Figure out the color and position of all four marbles and you'll crack the code! Are you good enough for the Extreme level?
Instructions[]
At the menu there are four levels to chose from,
Easy - Green and Orange marbles (3:00)
Medium - Green, Blue, and Orange marbles (3:00)
Hard - Green, Blue, Orange, and Black marbles (4:00)
Extreme - Green, Blue, Orange, Black, and Red marbles (5:00)
Once you're in the game, there are four holes for the marbles. You have to try to find out the exact pattern of them, which is hidden at the top. You click on a marble to select it, then click on the hole you want to put it in. After all the slots are filled, press check. On the right you'll see larger holes with small ones in them, and after you click check black or white marbles will appear. Black means that a marble is the correct color and is in the correct place. White means that a marble is the correct color, but is not in the correct place. After you clear a board, you will move to a different one. You have 8 tries to figure it out, and and have a limited ammout of time (see above), so be careful!
Medals