'Fractal Tree - for Run Basic - 29 Apr 2018
 'from BASIC256 - http://rosettacode.org/wiki/Fractal_tree#BASIC256
 'copy this text and go to http://www.runbasic.com

WindowWidth  = 500  'Run Basic max size 800 x 600
WindowHeight = 350
c = 255  '255 for white '0 for black

 graphic #w, WindowWidth, WindowHeight
 #w cls("black")  'black background color
 #w color(c,c,c)  'changes color to white

level = 10             ' initial values
leng = 50		
x = 230: y = 325       ' initial values x = 230: y = 285
pi = 3.1415			
rotation = 3.1415/2

'A1 = pi/27 : A2 = pi/8	    ' constants which determine shape
'C1 = 0.7 : C2 = 0.85       ' tree is drifted left

A1 = pi/9 : A2 = pi/9	' constants which determine shape
C1 = 0.85 : C2 = 0.85   ' Symmetrical Tree

dim xs(level+1) : dim ys(level+1)	' stacks

print : print "Welcome to the Run BASIC Fractal Tree Program"
#w color("green") 'color green
gosub [tree]
 render #w
' imgsave "Fractal_tree_BASIC-256.png", "PNG"
Print "Thank you and goodbye"
end

[tree]
	xs(level) = x : ys(level) = y
	gosub [putline]
	if level>0 then
		level = level - 1
		leng = leng*C1
		rotation = rotation - A1
		gosub [tree]
		leng = leng/C1*C2
		rotation = rotation + A1 + A2
		gosub [tree]
		rotation = rotation - A2
		leng = leng/C2
		level = level + 1
	end if
	x = xs(level) : y = ys(level)
	return

[putline]
	yn = -1*sin(rotation)*leng + y
	xn = cos(rotation)*leng + x
                #w line(x,y,xn,yn)
	x = xn : y = yn
	return
'end of code
End