PROC_block(x,y,size,r,g,b,dimmer)

copy and paste this program in BBC BASIC and run. I have placed lots of information in the code.
Have fun making depth shaded blocks.

     MODE 8
     REM r-red   g-green   b-blue
     REM         x , y ,size,r,  g,  b,dimmer  '
     PROC_block(500,500,40,100,200,100,2)
     REM remember that r,g,b is used to mix colors
     REM if you need help mixing colors, try the color mixer utility
     REM I will provide the tool in same place you found this soon
     END

     REM-------( x , y ,size,r,g,b,dimmer):dimmer is color reduction shading
     DEF PROC_block(x,y,s,r,g,b,d)
     LOCAL p,yc
     p=s/2
     FOR yc=1 TO s
       COLOUR 0,r,g,b:GCOL 0
       LINE x-yc,y-yc,x+yc,y-yc
       LINE x+yc,y-yc,x+yc,y+yc
       LINE x+yc,y+yc,x-yc,y+yc
       LINE x-yc,y+yc,x-yc,y-yc
       r=r-d
       g=g-d
       IF r<2 THEN r=2
       IF g<2 THEN g=2
       IF b<2 THEN b=2
       p=p-1
     NEXT yc
     COLOUR 0,0,0,0:REM returns 0 back to its original state
     ENDPROC