;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;This code will measure the displacement distance (signed)
;;of the sprite. The purpose is so that when making moving
;;platforms, you can have an x or y speed not multiple of
;;+/- #$10 without the need of lookup tables to move the player
;;relative with it. It does this by subtracting its final
;;position from its current position and using that value
;;to add it to the player's position.
;;
;;NOTE: If you plan to have the player spawn ON a platform when
;;the level loads, I recommend also using this subroutine since
;;the freeram does not clear automatically, causing the player
;;to "teleport".
;;
;;Output (when routine is done):
;;
;;$00 = [2 bytes], X position displacement
;;$02 = [2 bytes], Y position displacement
;;
;;
!TableSize		= 12
;;^Max amount of sprites processed in decimal. 12 for
;;regular ROM, 22 for SA-1. This is also the table size
;;in bytes.
;;
!Freeram_SavedXPosL	= $7F8327
!Freeram_SavedXPosH	= $7FC7BD
!Freeram_SavedYPosL	= $7FC7D3
!Freeram_SavedYPosH	= $7FC7E9
;;^Their size depends on !TableSize
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
MeasureDisplacement:
	LDA !Freeram_SavedXPosH,x	;\Store previous X position into $00
	XBA				;|
	LDA !Freeram_SavedXPosL,x	;|
	REP #$20			;|
	STA $00				;|
	SEP #$20			;/
	LDA $14E0,x			;\Load current X position into A
	XBA				;|
	LDA $E4,x			;/
	REP #$20			;\final position subtract by inital
	SEC				;|position = displacement stored in $00
	SBC $00				;|its signed, so if it moves left,
	STA $00				;|its gunna be negative.
	SEP #$20			;/


	LDA !Freeram_SavedYPosH,x	;\Store previous Y position into $02
	XBA				;|
	LDA !Freeram_SavedYPosL,x	;|
	REP #$20			;|
	STA $02				;|
	SEP #$20			;/
	LDA $14D4,x			;\Load current Y position into A
	XBA				;|
	LDA $D8,x			;/
	REP #$20			;\final position subtract by inital
	SEC				;|position = displacement stored in $02
	SBC $02				;|its signed, so if it moves up,
	STA $02				;|its gunna be negative.
	SEP #$20			;/

;This is so that if the sprite moves again for the 3rd frame.
	LDA $E4,x			;\update for next X position displacement
	STA !Freeram_SavedXPosL,x	;|
	LDA $14E0			;|
	STA !Freeram_SavedXPosH,x	;/
	LDA $D8,x			;\update for next Y position displacement
	STA !Freeram_SavedYPosL,x	;|
	LDA $14D4,x			;|
	STA !Freeram_SavedYPosH,x	;/
	RTS