sprite.asm

  org &4000
  run &4000

  di
  im 1

  ; set ei, ret to &38 interrupt
  ld a, &fb
  ld (&38), a
  ld a, &c9
  ld (&39), a
  ei

;; disable roms set mode 1
  ld bc, &7f8d
  out (c), c

;; clear both screen banks
  ld hl, &c000
  ld de, &8000
  xor a
.clear_screen
  ld (hl), a
  ld (de), a
  inc hl
  inc de
  cp h
  jp nz, clear_screen

  ;; generate screen address table from 0x0000 to 0x4000
  ld de, scr_addr_table
  call GenScrAddrs

  ld hl, dir_x
  ld (hl), 1
  ld hl, dir_y
  ld (hl), 1

  ld hl, screen_offset
  ld (hl), &c0

loop:

  ;; wait until vsync
  ld b, &f5
  in a, (c)
  rra
  jp nc, $-3

  ;; set border color
  ld bc, &7f10
  out (c), c
  ld c, &56
  out (c), c

  ld hl, pos_x
  ld a, (hl)
  ld hl, prev_x
  ld (hl), a

  ld hl, pos_y
  ld a, (hl)
  ld hl, prev_y
  ld (hl), a

  ld hl, pos_x
  ld b, (hl)
  ld hl, pos_y
  ld c, (hl)
  exx
  ld b, 6
  ld c, 32
  exx
;  call FillRect

  ld hl, pos_x
  ld a, (hl)
  ld hl, dir_x
  ld b ,(hl)
  add b
  ld hl, pos_x
  ld (hl), a
  ld b, 80-6
  cp b
  jp nz, skip_change_dir_x
  ld hl, dir_x
  ld (hl), -1
  jp done_change_dir_x
.skip_change_dir_x
  or a
  jp nz, done_change_dir_x
  ld hl, dir_x
  ld (hl), 1
.done_change_dir_x

  ld hl, pos_y
  ld a, (hl)
  ld hl, dir_y
  ld b ,(hl)
  add b
  ld hl, pos_y
  ld (hl), a
  ld b, 200-32
  cp b
  jp nz, skip_change_dir_y
  ld hl, dir_y
  ld (hl), -1
  jp done_change_dir_y
.skip_change_dir_y
  or a
  jp nz, done_change_dir_y
  ld hl, dir_y
  ld (hl), 1
.done_change_dir_y

  ld hl, CurSprite
  ld de, Sprite1
  ld (hl), e
  inc hl
  ld (hl), d


  ld hl, pos_x
  ld b, (hl)
  ld hl, pos_y
  ld c, (hl)
  exx
  ld b, 6
  ld c, 32
  exx
  call PutSprite

  ld bc, &7f10
  out (c), c
  ld c, &54
  out (c), c

  ld bc, &bc00+12
  out (c), c
  inc b
  ld hl, screen_offset
  ld a, (hl)
  cp &c0
  jr z, screen_offset_set_80
  ld a, &20
  jr screen_offset_done
.screen_offset_set_80
  ld a, &30
  ld c, a
.screen_offset_done
  ;out (c), a
  ;ld (hl), a
  jp loop

delay:
  dec a
  jp nz, delay
  ret

stack:
  ds 2

;; x, y, w, h
;; B: x
;; C: y
;; B': W
;; C'; H
;; CurSprite
PutSprite:

  ld l, c
  ld h, 0		; hl = Y
  add hl, hl		; multiply by 2
  ld de, scr_addr_table
  add hl, de	; add screen lookup
  ld a, (hl)
  inc hl
  ld h, (hl)
  ld l, a		; hl = screen y addr
  ld e, b		; de = Screen x
  ld d, 0
  add hl, de
  ex de, hl		; de = screen addr
  exx
  ld a, b
  exx  
  ld c, a		; bc = Sprite width
  ld b, 0
  ld hl, CurSprite
  ld a, (hl)
  inc hl
  ld h, (hl)
  ld l, a		; hl = Sprite Address

  exx
  ld l, c
  ld h, 0		; hl' = Sprite height
  exx
.PutSprite_L1
  push hl
  push de
  push bc

  exx
  ld de, screen_offset
  ld a, (de)
  exx
  ex de, hl
  add h
  ld h, a		; hl = &c000 + screen addr
  ex de, hl		; de = hl

  ldir
  pop bc
  pop de
  pop hl

  ex de, hl
  push bc
  push de

  exx
  ld de, screen_offset
  ld a, (de)
  exx
  ld d, a
  ld a, h
  sub d
  ld h, a  
  call GetNextLine	; hl = next screen line
  
  exx
  ld a, (de)
  exx
  add h
  ld h, a

  pop de
  pop bc
  ex de, hl

  add hl, bc	; hl = next sprite line

  exx
  dec l
  ret z
  exx

  jr PutSprite_L1

  ret
CurSprite:
  ds 2

; x, y, w, h
FillRect:

  ld l, c
  ld h, 0		; hl = Y
  add hl, hl		; multiply by 2
  ld de, scr_addr_table
  add hl, de	; add screen lookup
  ld a, (hl)
  inc hl
  ld h, (hl)
  ld l, a		; hl = screen y addr
  ld e, b		; de = Screen x
  ld d, 0
  add hl, de	; hl = pixel addr
  exx
  ld a, b
  exx  
  ld c, a		; bc = Sprite width
  ld b, 0
  exx
  ld a, c
  exx
  ld e, a
  ld d, 0		; de = Sprite height

.FillRect_L1
  push hl
  push de
  push bc

  exx
  ld de, screen_offset
  ld a, (de)
  exx
  add h
  ld h, a		; hl = &c000 + screen addr

.FillRect_L2
  ld a, 0
  ld (hl), a
  inc hl
  dec bc
  xor b
  cp c
  jr nz, FillRect_L2
  cp b
  jr nz, FillRect_L2

  pop bc
  pop de
  pop hl

  push bc
  push de

  exx
  ld de, screen_offset
  ld a, (de)
  exx
  ld d, a
  call GetNextLine	; hl = next screen line

  pop de
  pop bc

  dec e

  jr nz, FillRect_L1

  ret

;; HL current address
;; D screen offset
GetNextLine:
  ld a, h
  add &08		; add next line
  ld h, a	

  bit 6, h		; check overflow
  ret nz

  ld e, &50	; add offset
  add hl, de
  ret


;; DE Sprite Address
;; BC Sprite size
FillSprite:
  ld a, c
  ld (de), a
  inc de
  dec bc
  ld l, 0
  ld h, l
  or a
  sbc hl, bc
  add hl, bc
  jr nz, FillSprite
  ret

;; DE memory addr for LUT
GenScrAddrs:
  ld hl, 0

  exx
  ld c, 199
  exx
.GenScrAddrLoop
  ld a, h
  add &08
  ld h, a

  bit 6, h
  jr z, GenScrAddrSkipRow
  res 6, h
  ld bc, &0050
  add hl, bc

.GenScrAddrSkipRow
  exx
  dec c
  ret z
  exx

  ld a, l
  ld (de), a
  inc de
  ld a, h
  ld (de), a
  inc de

  jr GenScrAddrLoop  

pos_x: ds 1
pos_y: ds 1

prev_x: ds 1
prev_y: ds 1

dir_x: ds 1
dir_y: ds 1

screen_offset: ds 1

Sprite1:


db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &03, &0e, &00, &00, &00, &01, &0f, &0f
db &08, &00, &00, &03, &0e, &0f, &0c, &00, &00, &01, &00, &01, &0c, &00, &00, &00
db &00, &01, &0c, &00, &00, &00, &00, &00, &0e, &00, &00, &00, &03, &0f, &0e, &00
db &00, &00, &0f, &0f, &0e, &00, &00, &03, &0c, &00, &0e, &00, &00, &03, &08, &00
db &0e, &00, &00, &07, &00, &00, &0e, &00, &00, &07, &00, &01, &0e, &00, &00, &07
db &08, &07, &0e, &00, &00, &03, &0f, &0e, &0e, &00, &00, &01, &0f, &08, &0e, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00
db &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00, &00

Sprite1_Size equ $-Sprite1

align 2
scr_addr_table:
  ds 200*2