```Hello friends, my mind is blowing up in flames. I can't understand how
recursion works in this certainly case( this is part of 'Learn to
program' of Chris Pine ):

M = 'land'
o = 'water'

world = [
[o,o,o,o,o,M,o,o,o,o,o],
[o,o,o,o,M,M,o,o,o,o,o],
[o,o,o,o,o,M,o,o,M,M,o],
[o,o,o,M,o,M,o,o,o,M,o],
[o,o,o,o,o,M,M,o,o,o,o],
[o,o,o,o,M,M,M,M,o,o,o],
[M,M,M,M,M,M,M,M,M,M,M],
[o,o,o,M,M,o,M,M,M,o,o],
[o,o,o,o,o,o,M,M,o,o,o],
[o,M,o,o,o,M,M,o,o,o,o],
[o,o,o,o,o,M,o,o,o,o,o]]

def continent_size world, x ,y

if x < 0 or x > 10 or y < 0 or y > 10
return 0
end

if world[y][x] != 'land'
return 0
end

size = 1
world [y][x] = 'counted land'

size = size + continent_size(world, x-1, y-1)
size = size + continent_size(world, x , y-1)
size = size + continent_size(world, x+1, y-1)
size = size + continent_size(world, x-1, y )
size = size + continent_size(world, x+1, y )
size = size + continent_size(world, x-1, y+1)
size = size + continent_size(world, x , y+1)
size = size + continent_size(world, x+1, y+1)
size

end

puts continent_size(world, 5, 5)
#result is 32

I can't figure out how the program "counts" the M's, can't understand
in what part size = size + a_number( guess it must be 1(?). I guess this
is not easy to explain, by the way if you can give me a hand I'll take