Objective: 

Remove as many squares as you can.
Swap coloured squares the area around the square you move is affected.

For example:

R = red
G = green
B = blue
X = Blank

Affected area:

RRG
BGR
GBB

If you replace the central Green with a Red square you would remove the following Red squares.

XXG
BXX
GBB

If you get 3 combos you will received a special move

Special Moves: 

[a] Remove all selected colours for the entire grid
[y] Remove all colours in selected Row
[b] Remove all colours in selected Columns