10 REM ============================================================
   20 REM  BBC BASIC port of PMD-85 BASIC-G demo  (demo0-c.rmm)
   30 REM  Original: Tesla PMD 85-1, BASIC-G v1.0, RGB colour demo
   40 REM  A 3x3 grid of boxes with maths curves, each in its own colour.
   50 REM  Ported to BBC BASIC (MODE 1, 4 colours) - colour feature kept.
   60 REM ============================================================
   70 REM --- Coordinate mapping -------------------------------------
   80 REM  PMD-85 logical SCALE was 0..286 (x) by 0..256 (y).
   90 REM  BBC MODE 1 logical screen is 1280 x 1024 graphics units.
  100 REM  SX,SY scale PMD units -> BBC units.  PI held in K as original.
  110 MODE 1
  120 K=3.14159
  130 SX=1280/286 : SY=1024/256
  140 REM  COL(c) selects one of the 4 RGB colours (PMD POKE AD,c*64).
  150 REM  MODE 1 logical colours: 0=black 1=red 2=yellow 3=white.
  160 REM ------------------------------------------------------------
  170 REM  Define graphics helpers that apply the PMD->BBC scaling.
  180 REM  PROCmove / PROCdraw take PMD-85 logical coordinates.
  190 REM ------------------------------------------------------------
  200 :
  210 REM ================= MAIN (original line 4 = label 1000) =======
  220 REPEAT
  230   GCOL 0,3 : CLG                     : REM start in white, clear
  240   REM --- 3x3 grid of boxes (orig lines 5-11) ---
  250   FOR A=1 TO 193 STEP 96
  260     FOR B=1 TO 173 STEP 86
  270       PROCmove(A,B)
  280       PROCdraw(A+93,B)
  290       PROCdraw(A+93,B+83)
  300       PROCdraw(A,B+83)
  310       PROCdraw(A,B)
  320     NEXT B
  330   NEXT A
  340   REM --- centre labels (orig lines 12-16) ---
  350   PROCmove(105,139) : PROClabel(2,"PMD-85")
  360   PROCmove(107,126) : PROClabel(1,"RGB-GRAPHIC")
  370   PROCmove(110,105) : PROClabel(2,"BASIC")
  380   REM --- axes in box 1 (orig lines 17-23) ---
  390   PROCmove(3,195)   : PROCdraw(91,195)
  400   PROCmove(48,176)  : PROCdraw(48,251)
  410   REM --- COLOUR 1: sinc curve SIN(F)/F (orig 24-27) ---
  420   GCOL 0,1
  430   FOR F=-2.5*K TO 2.5*K STEP K/8
  440     H=4+(F+2.5*K)*89/(5*K)
  450     IF F=0 THEN S=1 ELSE S=SIN(F)/F
  460     IF F=-2.5*K THEN PROCmove(H,195+S*55) ELSE PROCdraw(H,195+S*55)
  470   NEXT F
  480   REM --- box 2 axes + sine wave (orig 28-36) ---
  490   GCOL 0,3
  500   PROCmove(240,2)   : PROCdraw(240,82)
  510   PROCmove(195,42)  : PROCdraw(284,42)
  520   GCOL 0,2
  530   FOR F=0 TO 4*K+.2 STEP K/12
  540     X=195+F*90/(4*K) : Y=38*SIN(F)+42
  550     IF F=0 THEN PROCmove(X,Y) ELSE PROCdraw(X,Y)
  560   NEXT F
  570   REM --- lower-left grid lines (orig 32-36) ---
  580   GCOL 0,3
  590   FOR A=7 TO 84 STEP 8  : PROCmove(1,A)  : PROCdraw(94,A)  : NEXT A
  600   FOR B=7 TO 94 STEP 9  : PROCmove(B,1)  : PROCdraw(B,84)  : NEXT B
  610   REM --- COLOUR 3: circle (orig 37-40) ---
  620   GCOL 0,3
  630   FOR F=0 TO 2*K STEP K/36
  640     A=30*SIN(F)
  650     IF F=0 THEN PROCmove(240+A,213) ELSE PROCdraw(240+A,213+36*COS(F))
  660   NEXT F
  670   REM --- COLOUR 0->use 1: Lissajous/rose COS(5F),SIN(3F) (orig 42-43) ---
  680   GCOL 0,1
  690   FOR F=0 TO 2*K STEP K/72
  700     X=144+40*COS(5*F) : Y=215+35*SIN(3*F)
  710     IF F=0 THEN PROCmove(X,Y) ELSE PROCdraw(X,Y)
  720   NEXT F
  730   REM --- COLOUR 1: spirograph/star burst (orig 44-50) ---
  740   GCOL 0,2
  750   FOR F=0 TO 26*K STEP K/1.27
  760     X=144+35*SIN(F) : Y=41+35*COS(F)
  770     IF F=0 THEN PROCmove(X,Y) ELSE PROCdraw(X,Y)
  780   NEXT F
  790   FOR F=0 TO 2*K STEP K/4
  800     FOR G=F-K/4 TO 2*K STEP K/4
  810       PROCmove(48+38*SIN(F),127+38*COS(F))
  820       PROCdraw(48+38*SIN(F+G),127+38*COS(F+G))
  830     NEXT G
  840   NEXT F
  850   REM --- COLOUR 3: spiral (orig 50-53) ---
  860   GCOL 0,3
  870   R=.1
  880   PROCmove(240,127)
  890   FOR F=0 TO 27.2 STEP K/24
  900     PROCdraw(240+R*SIN(F),127+R*COS(F))
  910     R=R+.2
  920   NEXT F
  930   REM --- final label + pause, then loop (orig 54) ---
  940   GCOL 0,3
  950   PROCmove(97,87) : PROClabel(1,"1")
  960   T=TIME : REPEAT UNTIL TIME-T>300   : REM PAUSE 60 (~3 s)
  970 UNTIL FALSE
  980 END
  990 :
 1000 DEF PROCmove(x,y) : MOVE x*SX, y*SY : ENDPROC
 1010 DEF PROCdraw(x,y) : DRAW x*SX, y*SY : ENDPROC
 1020 :
 1030 REM  PROClabel: print text at current graphics cursor.
 1040 REM  VDU 5 joins text output to the graphics cursor.
 1050 REM  BBC chars are ~32x32 graphics units; "sz" doubles spacing only
 1060 REM  (BBC BASIC has no built-in text magnification, so size is
 1070 REM   approximated - text is placed at the PMD label position).
 1080 DEF PROClabel(sz,t$)
 1090 VDU 5
 1100 PRINT t$;
 1110 VDU 4
 1120 ENDPROC