define RED = "\e[1;31m"
define YELLOW = "\e[1;33m"
define GREEN = "\e[1;32m"
 
define DIRS = [
    [-1, -1], [0, -1], [1, -1],
    [-1,  0],          [1,  0],
    [-1,  1], [0,  1], [1,  1],
]
 
enum (Empty, Tree, Heating, Burning)
define pix = [' ', GREEN + "*", YELLOW + "*", RED + "*"]
 
class Forest(p=0.01, f=0.001, height, width) {
 
    has coords = []
    has spot = []
    has neighbors = []
 
    method init {
        coords = (0..height ~X 0..width)
        spot = height.of { width.of { [true, false].pick ? Tree : Empty } }
        self.init_neighbors
    }
 
    method init_neighbors {
        for i,j in coords {
            neighbors[i][j] = gather {
                for dir in DIRS {
                    take(\(spot[i + dir[0]][j + dir[1]] \\ next))
                 }
            }
        }
    }
 
    method step {
        var heat = []
 
        for i,j in coords {
            given (spot[i][j]) {
                when Empty   { spot[i][j] = Tree    if (1.rand < p) }
                when Tree    { spot[i][j] = Heating if (1.rand < f) }
                when Heating { spot[i][j] = Burning; heat << [i, j] }
                when Burning { spot[i][j] = Empty }
            }
        }
 
        for i,j in heat {
            neighbors[i][j].each { |ref|
                *ref = Heating if (*ref == Tree)
            }
        }
    }
 
    method show {
        for i in ^height {
            say pix[spot[i]]
        }
    }
}

STDOUT.autoflush(true)
var(height, width) = `stty size`.nums.map{.dec}...
 
var forest = Forest(height: height, width: width)
print "\e[2J"

loop {
    print "\e[H"
    forest.show
    forest.step
}