100 PROGRAM DragonCurve
110 DECLARE SUB Dragon
120 SET WINDOW 0, 639, 0, 399
130 SET AREA COLOR 1
140 SET COLOR MIX(1) 0, 0, 0
150 REM SIN, COS in arrays for PI/4 multipl.
160 DIM S(0 TO 7), C(0 TO 7)
170 LET QPI = PI / 4
180 FOR I = 0 TO 7
190    LET S(I) = SIN(I * QPI)
200    LET C(I) = COS(I * QPI)
210 NEXT I
220 REM ** Initialize variables non-local for SUB Dragon.
230 LET SQ = SQR(2)
240 LET X = 224
250 LET Y = 140
260 LET RotQPi = 0
270 CALL Dragon(256, 15, 1) ! Insize = 2^WHOLE_NUM (looks better)
280 REM ** Subprogram
290 SUB Dragon (Insize, Level, RQ)
300    IF Level <= 1 THEN
310       LET XN = C(RotQPi) * Insize + X
320       LET YN = S(RotQPi) * Insize + Y
330       PLOT LINES: X, 399 - Y; XN, 399 - YN
340       LET X = XN
350       LET Y = YN
360    ELSE
370       LET RotQPi = MOD((RotQPi + RQ), 8)
380       CALL Dragon(Insize / SQ, Level - 1, 1)
390       LET RotQPi = MOD((RotQPi - RQ * 2), 8)
400       CALL Dragon(Insize / SQ, Level - 1, -1)
410       LET RotQPi = MOD((RotQPi + RQ), 8)
420    END IF
430 END SUB
440 END