;Let's say that there are 256 16x16 tiles, with 4 bytes each:
;00 01
;02 03
;Each screen is 16x12 tiles (to make room for possible HUD).
;+--+--+-
;|00|01|.
;+--+--+-
;|10|11|.
;+--+--+-
;|..|..|.
;After the tile data is the palette data.
;+-----+-
;|     |.
;| $FF |.
;|     |.
;+-----+-
;|.....|.
;That will take up a lot of space, so let's compress it:
;CLLLLLLL
;C: Codec to use
;L: Length stored plus 1 (0 is pointless)
;C values:
;0: Literal bytes, L bytes follow.
;1: Run-length bytes, L bytes are written, all with the next byte's value.
;At $BE00-$BFFF are the pointers to the 256 screens
;Low byte of each pointer is $BE00-$BEFF
;High byte of each pointer is $BF00-$BFFF
;All this data starts at $8000 in our ROM, ends at $BFFF.
;Things like collision (properties) are not discussed, sorry.
	.ORG $C000			;Start of code
	LDA #$10			;Initialize PPU registers here
	STA $2000
	LDA #$0A
	STA $2001
	LDA #$00
	STA $2005
	STA $2005
	LDY $FF				;Initialize other variables
	LDA #$00
	STA $04
	STA $06
	LDA #$BE
	STA $05
	LDA #$BF
	STA $07
	LDA ($04),Y			;$FF stores the room you want to load.
	STA $00
	LDA #$00
	STA $02
	LDA ($05),Y
	STA $01
	LDA #$60
	STA $03
	LDY #$00			;Initialize decompression loop
DECOM:	CPY #$F0			;Decompress!
	BEQ TSET
	LDA ($00),Y				
	AND #$80
	BEQ LIT
	BNE RLE
LIT:	LDA ($00),Y
	AND #$7F
	TAX
	INX
LITL:	INY
	LDA ($00),Y
	STA ($02),Y
	DEX
	BEQ LITL
	JMP DECOM
RLE:	LDA ($00),Y
	AND #$7F
	TAX
	INX
	INY
	LDA ($00),Y
RLEL:	STA ($02),Y
	INY
	DEX
	BEQ RLEL
	JMP DECOM
TSET:	LDA #$20			;Load tiles! (Tile indices are at $6000)
	STA $2006
	LDA #$00
	STA $2006
	STA $10
	STA $12
	STA $14
	STA $16
	LDA #$80
	STA $11
	LDA #$81
	STA $13
	LDA #$82
	STA $15
	LDA #$83
	STA $17
	LDX #$00
TEST:	TXA
	AND #$21
	BEQ TM00
	CMP #$01
	BEQ TM01
	TXA
	AND #$21
	CMP #$20
	BEQ TM02
	TXA
	AND #$21
	CMP #$21
	BEQ TM03
	JMP END
TM00:	TXA
	AND #$1E
	LSR
	STA $BF
	TXA
	AND #$C0
	LSR
	LSR
	CLC
	ADC $BF
	TAY
	LDA ($02),Y
	TAY
	LDA ($10),Y
	STA $2007
	INX
	JMP TEST
TM01:	TXA
	AND #$1E
	LSR
	STA $BF
	TXA
	AND #$C0
	LSR
	LSR
	CLC
	ADC $BF
	TAY
	LDA ($02),Y
	TAY
	LDA ($12),Y
	STA $2007
	INX
	JMP TEST
TM02:	TXA
	AND #$1E
	LSR
	STA $BF
	TXA
	AND #$C0
	LSR
	LSR
	CLC
	ADC $BF
	TAY
	LDA ($02),Y
	TAY
	LDA ($14),Y
	STA $2007
	INX
	JMP TEST
TM03:	TXA
	AND #$1E
	LSR
	STA $BF
	TXA
	AND #$C0
	LSR
	LSR
	CLC
	ADC $BF
	TAY
	LDA ($02),Y
	TAY
	LDA ($16),Y
	STA $2007
	INX
	JMP TEST
END:	RTS