[Game Play]
A stack is built from pieces of matching colour blocks.
Swap neighbouring blocks to create pieces with only four blocks.
The tetrominos remove to cascade the remaining pieces and score.
Tetrominos may be created in cascades for bonus.
Stacked pieces may create larger pieces of matching colour. Break
up larger pieces by swapping to create pieces with only four blocks.
Pieces are scrolled from the base of the stack.
Clear level to progress to the next round before the stack reaches
the top.
[Controls]
Tap or scroll to select a block.
Fling to swap neighbouring blocks in the horizontal or
vertical direction.