The game is played on a 6×6 grid of symbols. After every tumble, one more reel or row of symbols opens up, extending the grid, in the following order: bottom row, top row, right reel and lastly left reel. After all sides are unlocked, the grid remains 8×8 until the end of all tumbles resulted from the current spin.
This is the SCATTER symbol.
This is the WILD symbol and substitutes for all symbols except for SCATTER. It can appear on all reels.