Mission of Flood Fill is to fill each piece of the area with one of the 4 colors but don't let the same colors touch. Touch a shape with your mouse to fill it and use 1, 2, 3 and 4 to switch colors.
Click with the mouse to fill in the colours.
Use the 1,2,3,4 keys to select the colors or click on them with the mouse.
Don't let the same colors touch!