N = 150 : M = 150 : P = 0.03 : F = 0.00003

dim f(N+2,M+2) # 1 tree, 0 empty, 2 fire
dim fn(N+2,M+2)
graphsize N,M
fastgraphics

for x = 1 to N
	for y = 1 to M
		if rand<0.5 then f[x,y] = 1
	next y
next x

while True
	for x = 1 to N
		for y = 1 to M
			if not f[x,y] and rand<P then fn[x,y]=1
			if f[x,y]=2 then fn[x,y]=0
			if f[x,y]=1 then
				fn[x,y] = 1
				if f[x-1,y-1]=2 or f[x,y-1]=2 or f[x+1,y-1]=2 then fn[x,y]=2
				if f[x-1,y]=2 or f[x+1,y]=2 or rand<F then fn[x,y]=2
				if f[x-1,y+1]=2 or f[x,y+1]=2 or f[x+1,y+1]=2 then fn[x,y]=2
			end if
			# Draw
			if fn[x,y]=0 then color black
			if fn[x,y]=1 then color green
			if fn[x,y]=2 then color yellow
			plot x-1,y-1
		next y
	next x
	refresh
	for x = 1 to N
		for y = 1 to M
			f[x,y] = fn[x,y]
		next y
	next x
end while