squareCount = 4
squareSize = 25

def setup():
  size(600, 600)

def draw():
    background(255)
    i = 1
    while i <= squareCount:
        j = 1
        while j <= squareCount:
            if (i + j) % 2 == 0:
                fill( 255, 0, 0, 100 )
            else:
                fill( 0, 0, 255, 100 )

            rect( j*100, i*100, squareSize,squareSize)
            j = j + 1

        i = i + 1


def keyPressed():
    global squareCount, squareSize
    if ( key == 'z' ):
        squareCount = squareCount - 1

    if ( key == 'x' ):
        squareCount = squareCount + 1

    if ( key == 'n' ):
        squareSize = squareSize - 5

    if ( key == 'm' ):
        squareSize = squareSize + 5