PROGRAM LSYS_CROSS_SQUARE   ! © W.van Duyn 27th April 2004
!also Mayan triangle at order 3
SET MODE "color"
SET WINDOW 0,1199,0,903
SET BACKGROUND COLOR "white"
CLEAR
CALL init
END

SUB init
OPTION ANGLE degrees
PRINT "input: x try 200, y try 100"
INPUT x,y
PRINT "input: Side try 600,level try 4, dimension try 4 or 3"
INPUT side,level,ak
CLEAR
SET COLOR 16
FLOOD 1,1
LET a=0
LET k=360/ak
LET r=4+2*COS(k) LET d=side/(r^level)
SET COLOR 12
FOR i=1 TO ak
CALL axiom(d,level,a,x,y,k)
NEXT i
END SUB

SUB axiom(d,level,a,x,y,k)
LET lev=level
CALL move(d,lev,a,x,y,k)
CALL turnLEFT(a,k)
END SUB

SUB move(d,lev,a,x,y,k)
IF lev=0 THEN
CALL travelON(d,a,x,y)
EXIT IF
ELSE
CALL move(d,lev-1,a,x,y,k)
CALL turnLEFT(a,k)
CALL move(d,lev-1,a,x,y,k)
CALL turnRIGHT(a,k)
CALL move(d,lev-1,a,x,y,k)
CALL move(d,lev-1,a,x,y,k)
CALL turnRIGHT(a,k)
CALL move(d,lev-1,a,x,y,k)
CALL turnLEFT(a,k)
CALL move(d,lev-1,a,x,y,k)
END IF
END SUB

SUB travelON(d,a,x,y)
OPTION ANGLE degrees
LET x2=x+d*cos(a)
LET y2=y+d*sin(a)
PLOT x,y;x2,y2
LET x=x2
LET y=y2
END SUB

SUB turnLEFT(a,k)
LET a=a+k
END SUB

SUB turnRIGHT(a,k)
LET a=a-k
END SUB