MovingBoxes.txt

REM MODE MODE   :REM Reset Screen display. but leave in current mode.
ON ERROR PRINTREPORT$;" at line ";ERL:END

REM START WITH GREY
GCOL ON 192,192,192

OFF         : REM Turn off text cursor
:
REM The following four line read the current screen size co-ords.
SYS "OS_ReadModeVariable",-1,4 TO ,,XEigFactor%
SYS "OS_ReadModeVariable",-1,5 TO ,,YEigFactor%
SYS "OS_ReadModeVariable",-1,11 TO ,,XSize%:XSize%+=1
SYS "OS_ReadModeVariable",-1,12 TO ,,YSize%:YSize%+=1
:

XStep%=1<<XEigFactor%
YStep%=1<<YEigFactor%
MaxX%=XSize%<<XEigFactor%
MaxY%=YSize%<<YEigFactor%
CentreX%=MaxX% DIV 2
CentreY%=MaxY% DIV 2

BSize% = 100
Step%= 12

B1Y%= CentreY%
B1X%= CentreX%- (4*BSize%)

B2Y% = CentreY%
B2X%= CentreX% + (4*BSize%)



REPEAT
      GCOL ON 128,128,128
      CLG
      GCOL 0,0,0
      PROCDrawBox( B1X%,B1Y%,BSize%)
      GCOL 255,255,255
      PROCDrawBox( B2X%,B2Y%,BSize%)

      B1X% += Step%
      B1Y% += Step%
      B2X% += Step%
      B2Y% += Step%

      IF B1X%>MaxX% THEN B1X% -= MaxX%
      IF B2X%>MaxX% THEN B2X% -= MaxX%

      IF B1Y%>MaxY% THEN B1Y% -= MaxY%
      IF B2Y%>MaxY% THEN B2Y% -= MaxY%

      WAIT
UNTIL FALSE


END

DEF PROCDrawBox(x%,y%,size%)
  MOVE x%-size%,y%
  MOVE x%-size%,y%+size%
  PLOT 85,x%,y%+size%

  MOVE x%+size%,y%+size%
  PLOT 85,x%+size%,y%

  MOVE  x%+size%,y%-size%
  PLOT  85, x%,y%-size%

  MOVE  x%-size%,y%-size%
  PLOT  85,x%-size%,y%

ENDPROC