_Title "Pythagoras Tree"

Dim As Integer sw, sh
sw = 640
sh = 480

Screen _NewImage(sw, sh, 32)

Call pythTree(sw / 2 - sw / 12, sh - 30, sw / 2 + sw / 12, sh - 30, 0)

Sleep
System

Sub pythTree (ax As Integer, ay As Integer, bx As Integer, by As Integer, depth As Integer)
    Dim As Single cx, cy, dx, dy, ex, ey
    Dim As Integer c

    cx = ax - ay + by
    cy = ax + ay - bx
    dx = bx + by - ay
    dy = ax - bx + by
    ex = (cx - cy + dx + dy) * 0.5
    ey = (cx + cy - dx + dy) * 0.5
    c = depth * 15
    Color _RGB(c Mod 256, Abs((255 - c)) Mod 256, (144 + c) Mod 256)
    Line (cx, cy)-(ax, ay)
    Line (ax, ay)-(bx, by)
    Line (bx, by)-(dx, dy)
    Line (dx, dy)-(cx, cy)
    Line (cx, cy)-(ex, ey)
    Line (ex, ey)-(dx, dy)
    If depth < 12 Then
        Call pythTree(cx, cy, ex, ey, depth + 1)
        Call pythTree(ex, ey, dx, dy, depth + 1)
    End If
End Sub