accesses

$FF11 -- sound mode (disable for now)
$FF47

 Name - BGP
 Contents - BG & Window Palette Data (R/W)
 Bit 7-6 - Data for Dot Data 11
 (Normally darkest color)
 Bit 5-4 - Data for Dot Data 10
 Bit 3-2 - Data for Dot Data 01
 Bit 1-0 - Data for Dot Data 00
 (Normally lightest color)
 This selects the shade of grays to use
 for the background (BG) & window pixels.
 Since each pixel uses 2 bits, the
 corresponding shade will be selected from
 here.

$FF42

 Name - SCY
 Contents - Scroll Y (R/W)
 8 Bit value $00-$FF to scroll BG Y screen
 position.

$FF40

 Name - LCDC (value $91 at reset)
 Contents - LCD Control (R/W)
 Bit 7 - LCD Control Operation *
 0: Stop completely (no picture on screen)
 1: operation
 Bit 6 - Window Tile Map Display Select
 0: $9800-$9BFF
 1: $9C00-$9FFF
 Bit 5 - Window Display
 0: off
 1: on
 Bit 4 - BG & Window Tile Data Select
 0: $8800-$97FF
 1: $8000-$8FFF <- Same area as OBJ
 Bit 3 - BG Tile Map Display Select
 0: $9800-$9BFF
 1: $9C00-$9FFF
 Bit 2 - OBJ (Sprite) Size
 0: 8*8
 1: 8*16 (width*height)
 Bit 1 - OBJ (Sprite) Display
 0: off
 1: on
 Bit 0 - BG & Window Display
 0: off
 1: on
 * - Stopping LCD operation (bit 7 from 1 to 0) must
 be performed during V-blank to work properly. V-
 blank can be confirmed when the value of LY is
 greater than or equal to 144.

$FF44

 Name - LY
 Contents - LCDC Y-Coordinate (R)
 The LY indicates the vertical line to which
 the present data is transferred to the LCD
 Driver. The LY can take on any value
 between 0 through 153. The values between
 144 and 153 indicate the V-Blank period.
 Writing will reset the counter.

$FF13 -- sound (disable for now)
$FF50 -- last instruction so it doesn't really matter