The key appears on the grid as soon as all the streams are completed correctly; you will guide Tyler in finding the right path on the blocks raised and to pick up the key. The Key is not a collectible item; it is only useful to unlock the next level, that's why it is not displayed in the inventory.
Many flows are sunk below the surface by restricting the area of movement. You can raise the floor by activating the levers. Sometimes, the levers, could be hidden or placed also in areas that are not always easy to reach. Use weapons and gadgets to find the Levers!
Destroy the crates with the Hand Weapon in order to find the Gadgets and collect them into your inventory. The Crate appears only in Single Player mode. In Multiplayer mode the gadgets are available in the inventory at the beginning of the game.
In the Dark World you can find some hidden levers into crates; you need to activate this lever to unlock the next puzzle. Do not forget to use the Teleport or Spawn to gain time.
