Arrow flash test (turtle construct color test) (BBC4W)

This is for testing on cross platform but at the moment only works properly on BBC Basic For Windows.
When it works on a specific BBCSDL platform, I will mention the platform on a list HERE:


     MODE 8
     REM lets construct the arrow interface color test:
     REM resetrgb is not necessary unless you are working with palettes
     REM it will be a part of things later and will be very necessary when mixing base colors and palettes
     PROCresetrgb
     r=0:xx=0:yy=0
     xx=100:yy=100

     REPEAT
       REM (x,y,angle,color)
       PROCarrow(xx,110,90,RND(15))
       PROCarrow(110,yy,270,RND(15))
       PROCarrow(110,yy+10,0,RND(15))
       PROCarrow(100,yy,180,RND(15))
     UNTIL FALSE
     END

     DEF PROCarrow(x,y,angle,c)
     PROCt("x",x):PROCt("y",y)
     REM PROCt("m",100)
     PROCt("a",angle)
     PROCt("d",1)
     PROCt("c",15)
     PROCt("f",25)
     PROCt("r",90)
     PROCt("f",5)
     PROCt("l",135)
     PROCt("f",25)
     PROCt("l",90)
     PROCt("f",25)
     PROCt("l",135)
     PROCt("f",5)
     PROCt("r",90)
     PROCt("f",25)
     PROCt("l",90)
     PROCt("f",25)
     PROCt("l",98)
     PROCt("u",0)
     PROCt("f",15)
     REM PROCt("d",0)
     PROCt("p",c)
     ENDPROC

     DEFPROCt(mess$,amt)
     PRIVATE angle,x,y,pen$,dracol,sz
     IF sz<1 THEN sz=1
     GCOL dracol
     IF pen$="" THEN pen$="down"
     IF mess$="a" THEN angle=amt
     IF mess$= "r" THEN angle=angle - amt
     IF mess$= "l" THEN angle=angle + amt
     IF mess$= "f" THEN VDU 23,23,sz|:PROC_turtle(amt,angle,pen$,x,y)
     IF mess$= "u" THEN pen$="up"
     IF mess$= "d" THEN pen$="down"
     IF mess$= "p" THEN
       GCOL 128+POINT(x,y)
       GCOL amt:FILL x,y
     ENDIF
     IF mess$= "c" THEN IF amt=16 THEN amt=0
     IF mess$= "c" THEN GCOL amt:dracol=amt
     IF mess$= "s" THEN sz=amt
     VDU 23,23,sz|
     IF mess$= "m" THEN
       x=amt:y=amt
       pen$="move"
     ENDIF
     IF mess$="x" THEN x=amt:pen$="move"
     IF mess$="y" THEN y=amt: pen$="move"
     PROC_turtle(0,angle,pen$,x,y)
     ENDPROC
     DEFPROC_turtle(coun,angle,pen$,RETURN x,RETURN y)
     PRIVATE sx,sy

     IF pen$="move" THEN sx=x:sy=y
     IF pen$="up" OR pen$="down" THEN
       sx+=coun*COS(RAD(angle))
       sy+=coun*SIN(RAD(angle))
       IF pen$="down" THEN LINE x,y,sx,sy
     ENDIF
     x=sx:y=sy
     ENDPROC
     DEFPROCresetrgb
     COLOUR 0,0,0,0 :COLOUR 1,200,0,0 :COLOUR 2,000,200,000
     COLOUR 3,200,200,000:COLOUR 4,000,000,200:COLOUR 5,200,000,200
     COLOUR 6,000,200,200:COLOUR 7,200,200,200:COLOUR 8,056,056,056
     COLOUR 9,248,056,056:COLOUR 10,056,248,056:COLOUR 11,248,248,056
     COLOUR 12,056,056,248:COLOUR 13,248,056,248:COLOUR 14,056,248,248
     COLOUR 15,248,248,248
     ENDPROC