dcb "INIT"
RTL

dcb "MAIN"
JSR SUB_GFX
RTL

;;;;;Graphics Routeine

FRAMES dcb $C2,$C0

SUB_GFX
JSR GET_DRAW_INFO

LDA $157C,x
STA $02

LDA $00
STA $0300,y

LDA $01
STA $0301,y

PHX
LDA $13
LSR A
LSR A
AND #$01
TAX
LDA FRAMES,x
STA $0302,y
PLX

LDA $15F6,x

PHX
LDX $02
BNE_NO_FLIP_1
ORA #$40
NO_FLIP_1
PLX

ORA $64
STA $0303,y

INY
INY
INY
INY

LDY #$02
LDA #$00
JSL $01B7B3
RTS

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;
; GET_DRAW_INFO
; This is a helper for the graphics routine.  It sets off screen flags, and sets up
; variables.  It will return with the following:
;
;		Y = index to sprite OAM ($300)
;		$00 = sprite x position relative to screen boarder
;		$01 = sprite y position relative to screen boarder  
;
; It is adapted from the subroutine at $03B760
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;

SPR_T1              dcb $0C,$1C
SPR_T2              dcb $01,$02

GET_DRAW_INFO       STZ $186C,x             ; reset sprite offscreen flag, vertical
                    STZ $15A0,x             ; reset sprite offscreen flag, horizontal
                    LDA $E4,x               ; \
                    CMP $1A                 ;  | set horizontal offscreen if necessary
                    LDA $14E0,x             ;  |
                    SBC $1B                 ;  |
                    BEQ ON_SCREEN_X         ;  |
                    INC $15A0,x             ; /

ON_SCREEN_X         LDA $14E0,x             ; \
                    XBA                     ;  |
                    LDA $E4,x               ;  |
                    REP #$20                ;  |
                    SEC                     ;  |
                    SBC $1A                 ;  | mark sprite invalid if far enough off screen
                    CLC                     ;  |
                    ADC.W #$0040            ;  |
                    CMP.W #$0180            ;  |
                    SEP #$20                ;  |
                    ROL A                   ;  |
                    AND #$01                ;  |
                    STA $15C4,x             ; / 
                    BNE INVALID             ; 
                    
                    LDY #$00                ; \ set up loop:
                    LDA $1662,x             ;  | 
                    AND #$20                ;  | if not smushed (1662 & 0x20), go through loop twice
                    BEQ ON_SCREEN_LOOP      ;  | else, go through loop once
                    INY                     ; / 
ON_SCREEN_LOOP      LDA $D8,x               ; \ 
                    CLC                     ;  | set vertical offscreen if necessary
                    ADC SPR_T1,y            ;  |
                    PHP                     ;  |
                    CMP $1C                 ;  | (vert screen boundry)
                    ROL $00                 ;  |
                    PLP                     ;  |
                    LDA $14D4,x             ;  | 
                    ADC #$00                ;  |
                    LSR $00                 ;  |
                    SBC $1D                 ;  |
                    BEQ ON_SCREEN_Y         ;  |
                    LDA $186C,x             ;  | (vert offscreen)
                    ORA SPR_T2,y            ;  |
                    STA $186C,x             ;  |
ON_SCREEN_Y         DEY                     ;  |
                    BPL ON_SCREEN_LOOP      ; /

                    LDY $15EA,x             ; get offset to sprite OAM
                    LDA $E4,x               ; \ 
                    SEC                     ;  | 
                    SBC $1A                 ;  | $00 = sprite x position relative to screen boarder
                    STA $00                 ; / 
                    LDA $D8,x               ; \ 
                    SEC                     ;  | 
                    SBC $1C                 ;  | $01 = sprite y position relative to screen boarder
                    STA $01                 ; / 
                    RTS                     ; return

INVALID             PLA                     ; \ return from *main gfx routine* subroutine...
                    PLA                     ;  |    ...(not just this subroutine)
                    RTS                     ; /