53249



     220 IF STICK(0)=13 THEN D=USR(DOWN,PM
         BASE+511+Y):Y=Y+1
     250 GOTO 210
     300 U=USR(UP,PMBASE+511+Y):Y=Y-l
     310 RETURN

     This will move any nine-line (or less) size player vertically with the
     joystick. If you have a larger player size, increase the 11 in line 140
     to a number two larger than the number of vertical lines the player
     uses, and change the ten in line 150 to one greater than the
     number of lines. To add horizontal movement, add the following
     lines:

     6     HPOS = 53248
     230   IF STICK(0) = 11 THEN X = X - 1:
           POKE HPOS, X
     240   IF STICK(0) = 7 THEN X = X + 1:
          POKE HPOS, X

     You can use the routine to move any player by changing the
     number 511 in the USR calls to one less than the start address of the
     object to be moved. See the appendix for a map of P/M graphics
     memory use. Missiles are more difficult to move vertically with this
     routine, since it moves an entire byte, not bits. It would be useful
     for moving all four missiles vertically if you need to do so; they
     could still be moved horizontally in an individual manner.
     See COMPUTE!, December 1981, February 1982, and May 1982,
     for some solutions and some machine language move routines, and
     COMPUTE!, October 1981, for a solution with animation involving
     P/M graphics.

                              M0PF
     (R) Missile 0 to playfield collision. This register will tell you which
     playfield the object has "collided" with, i.e., overlapped. If missile
     0 collides with playfield two, the register would read four and so
     on. Bit use is:

           Bit     7    6    5    4    3    2    1    0
     Playfield     .....unused.....    3    2    1    0
     Decimal       ................    8    4    2    1

53249          D00l           HOPSP1
     (W) Horizontal position of player 1.

                              M1PF
     (R) Missile 1 to playfield collision.

53250          D002           HPOSP2
     (W) Horizontal position of player 2.

                              M2PF