Let's Code MS DOS 0x1E: Power BASIC Snowflake

KOCH.BAS

DIM angle AS SHARED DOUBLE
DIM COL AS SHARED INTEGER
DIM SCALE AS SHARED DOUBLE

'-------------------------------------------------------------------
' Make a turn in the curve, given in degrees
'-------------------------------------------------------------------
SUB turn (degrees AS DOUBLE)
  angle = angle + degrees*3.14159265/180
END SUB

SUB minus
  turn 60
END SUB

SUB plus
  turn -60
END SUB

'-------------------------------------------------------------------
' Draws one step forward in the curve
'-------------------------------------------------------------------
SUB forward (length AS DOUBLE, col as INTEGER)
  LINE - STEP (COS(angle)*length, SIN(angle)*length), col
END SUB

'-------------------------------------------------------------------
' Draws a Koch curve
' - DEPTH : number of subdivisions
'-------------------------------------------------------------------
SUB KOCH(depth AS INTEGER)
  ' axiom of the Koch curve
  F depth
  minus
  minus
  F depth
  minus
  minus
  F depth
END SUB

'-------------------------------------------------------------------
' Draws one iteration of the Koch curve
'-------------------------------------------------------------------
SUB F (depth AS INTEGER)
  IF depth=0 THEN
    forward SCALE, col
  ELSE
    F depth-1
    plus
    F depth-1
    minus
    minus
    F depth-1
    plus
    F depth-1
  END IF
END SUB

'-------------------------------------------------------------------
' Main program
'-------------------------------------------------------------------

SCREEN 12
RANDOMIZE TIMER

angle = 0
count = 0
WHILE INSTAT = 0
  IF count > 100 THEN
    CLS
    COUNT = 0
  ELSE
    COUNT = COUNT + 1
  END IF
  DEPTH = 4   ' maximum recursion depth
  STRIDE = 5  ' length per line; needs to be bigger than depth
  SCALE = (STRIDE - DEPTH) * STRIDE * (0.2 + RND)
  X = -160 / SCALE + RND * 640
  Y = -120 / SCALE + RND * 480
  COL = 1 + INT(RND * 16)
  PSET (X,Y), COL
  KOCH(DEPTH)
  SLEEP 1
WEND

SCREEN 0