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⌂ ∞ Elite on the BBC Micro and NES

Drawing sprites: HideSprites

[NES version, Bank 7]

       Name: HideSprites                                             [Show more]
       Type: Subroutine
   Category: Drawing sprites
    Summary: Hide X sprites from sprite Y / 4 onwards

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * HideExplosionBurst calls HideSprites




 Arguments:

   X                    The number of sprites to hide

   Y                    The number of the first sprite to hide * 4



.HideSprites

 LDA #240               ; Set A to the y-coordinate that's just below the bottom
                        ; of the screen, so we can hide the required sprites by
                        ; moving them off-screen

.hspr1

 STA ySprite0,Y         ; Set the y-coordinate for sprite Y / 4 to 240 to hide
                        ; it (the division by four is because each sprite in the
                        ; sprite buffer has four bytes of data)

 INY                    ; Add 4 to Y so it points to the next sprite's data in
 INY                    ; the sprite buffer
 INY
 INY

 DEX                    ; Decrement the loop counter in X

 BNE hspr1              ; Loop back until we have hidden X sprites

 RTS                    ; Return from the subroutine

 EQUB $0C, $20, $1F     ; These bytes appear to be unused