Fog and volcano

Fog can block all kinds of pieces and it spreads on one more cell after each of your moves. You can stop the spreading or remove the fog by matching pieces of the same color, using bonuses, boosters, or animals' abilities next to it. The blocked pieces cannot be moved and aren't affected by the gravity.
The fog can be spawned by itself at the start of the level or can be generated during the level by the volcano. In the second case volcano blocks 3 pieces after each of your moves instead of one. To stop the volcano from generating the fog you need to match pieces of the same color, using bonuses, boosters, or animals' abilities next to it.