Bubble Object

; ---------------------------------------------------------------------------
; Object 19 - bubble from Sega Screen
; ---------------------------------------------------------------------------

Obj19:                  ; XREF: Obj_Index
        moveq   #0,d0
        move.b  $24(a0),d0
        move.w  Obj19_Index(pc,d0.w),d0
        jsr     Obj19_Index(pc,d0.w)
        jmp     DisplaySprite
; ===========================================================================
Obj19_Index:
        dc.w    Obj19_Main-Obj19_Index
        dc.w    Obj19_ToUp-Obj19_Index
; ===========================================================================
Obj19_Main:
        addi.b  #2,$24(a0)                  ; add 2 to routine number
        move.l  #Map_obj19,4(a0)            ; set mappings
        move.w  #$2AB,2(a0)                 ; set VRAM pointer
        move.b  #0,1(a0)                    ; set render parametrs
        move.b  #$13,$19(a0)                ; set "on object"
        move.b  #0,$18(a0)                  ; set priority back
        addq.l  #2,$FFFFF636                ; add 2 to frame counter
        jsr     RandomNumber                ; get pseudo-random number
        and.b   #%11111111,d0               ; get only 7 bits from number
        move.w  d0,8(a0)                    ; set X-position of bubble
        move.w  #400,$A(a0)                 ; set Y-position of bubble
        addq.l  #2,$FFFFF636                ; add 2 to frame counter
        jsr     RandomNumber                ; get pseudo-random number
        and.b   #3,d0                       ; get only 2 bits from number
        move.b  d0,$1A(a0)                  ; set size (or frame)
        move.w  8(a0),$30(a0)               ; copy X-position (need for waving)
        rts                                 ; return to subroutine

Obj19_ToUp:
        moveq   #0,d0                       ; clear d0
        move.w  $FFFFCC02,d0                ; move shift of first row of background
        add.w   #8,d0                       ; add 8 (need for center)
        bpl.s   @cont                       ; if plus, branch
        neg.w   d0                          ; negative number
@cont   add.w   $30(a0),d0                  ; add static copied X-position
        move.w  d0,8(a0)                    ; refresh X-position (waving)
        moveq   #0,d0                       ; clear d0
        move.b  $1A(a0),d0                  ; move size (or frame)
        addq.b  #1,d0                       ; add 1 to size
        sub.w   d0,$A(a0)                   ; subtract from Y-position
        bpl.s   @rts                        ; if bubble is on screen, branch
        addq.l  #2,$FFFFF636                ; add 2 to frame counter
        jsr     RandomNumber                ; get pseudo-random number
        and.b   #%11111111,d0               ; get only 7 bits from number
        move.w  d0,8(a0)                    ; set X-position of bubble
        move.w  #400,$A(a0)                 ; set Y-position of bubble
        addq.l  #2,$FFFFF636                ; add 2 to frame counter
        jsr     RandomNumber                ; get pseudo-random number
        and.b   #3,d0                       ; get only 2 bits from number
        move.b  d0,$1A(a0)                  ; set size (or frame)
@rts    rts
; ===========================================================================
; ---------------------------------------------------------------------------
; Sprite mappings - swinging ball on a chain from GHZ boss
; ---------------------------------------------------------------------------
Map_obj48:
    include "_maps\obj48.asm"

; ---------------------------------------------------------------------------
; Sprite mappings - bubbles from Sega Screen
; ---------------------------------------------------------------------------
Map_obj19:
    include "#SegaScreen\Bubbles_Map.asm"