level header format

  MUSIC_FLAGS1
;ad.mmmmm
;|| +++++- music
;|+------- if 1, player starts facing left
;+-------- if 1, use alternate buffer for collected bits
  XPOS
;xxxxxxxx
;++++++++- X position the player starts on
  YPOS_SCREENS
;ssssyyyy
;||||++++- Y position the player starts at
;++++----- number of screens in the level
  SPRITE_SLOT_1
;tttttttt sprite tileset 1
  SPRITE_SLOT_2
;tttttttt sprite tileset 2
  SPRITE_SLOT_3
;tttttttt sprite tileset 3
  SPRITE_SLOT_4
;tttttttt sprite tileset 4
  LEVEL_POINTER_LO
  LEVEL_POINTER_HI
  SPRITE_POINTER_LO
  SPRITE_POINTER_HI
  BACKGROUND_COLOR
.endenum
;uuuuuuuu - list of uploads to make for background tiles, palettes or whatever
;11111111 - ending with 255
;gets written to LevelUploadList

;hgfedcba Lonmlkji - boundaries between screens horizontally
;if L: specify links for top and bottom
;????nnnn
;||||++++- number of screens to change
;++++----- other flags that haven't been assigned anything
;ttttbbbb
;||||++++- bottom screen link
;++++----- top screen link

;Level data:
;TTTTTTTT XXXXYYYY [SSSSSSSS]
;T - Object type (0-255)
;Y - Y position absolute (0-15)
;X - X position relative (0-15)
;S - Settings byte, if needed
;
;Level commands
;1111TTTT [SSSSSSSS]
;T - 0 finished with the level
;    1 set X to S
;    2 write 1 column byte at current column
;    3 write 2 column bytes starting at this column
;    4 write 3 column bytes starting at this column
;    5 current X -= 16
;    6 current X += 16

---- level 1:

  .byt 0   ; music 0
  .byt 5   ; X pos 5
  .byt $25 ; 2 screens, start at Y pos 5
  .byt GraphicsUpload::SP_WALKER
  .byt GraphicsUpload::SP_CANNON
  .byt GraphicsUpload::SP_FIRE
  .byt GraphicsUpload::SP_KING
  .addr Level1Data
  .addr Level1Sprite
  .byt $31 ; background
  .byt GraphicsUpload::PAL_GRASSY
  .byt GraphicsUpload::BG_COMMON
  .byt GraphicsUpload::BG_GRASSY
  .byt 255
  .word %0000000000000000 ; boundaries