diff --git a/Makefile b/Makefile
index d493419..8aeba6c 100644
--- a/Makefile
+++ b/Makefile
@@ -41,9 +41,9 @@ ROM = $(BINDIR)/$(ROMNAME).$(ROMEXT)
 # Argument constants
 INCDIRS  = src/ src/include/
 WARNINGS = all extra
-ASFLAGS  = -p $(PADVALUE) $(addprefix -i,$(INCDIRS)) $(addprefix -W,$(WARNINGS))
-LDFLAGS  = -p $(PADVALUE)
-FIXFLAGS = -p $(PADVALUE) -v -i "$(GAMEID)" -k "$(LICENSEE)" -l $(OLDLIC) -m $(MBC) -n $(VERSION) -r $(SRAMSIZE) -t $(TITLE)
+ASFLAGS  = -p 0xFF $(addprefix -i,$(INCDIRS)) $(addprefix -W,$(WARNINGS))
+LDFLAGS  = -p 0xFF
+FIXFLAGS = -p 0xFF -l 0x33 -m 0x03 -r 0x02 -v -i $(GAMEID) -k $(LICENSEE) -t $(TITLE) -n $(VERSION)
 
 # The list of "root" ASM files that RGBASM will be invoked on
 SRCS = $(wildcard src/*.asm)
diff --git a/project.mk b/project.mk
index 7947a4b..d1afdee 100644
--- a/project.mk
+++ b/project.mk
@@ -1,13 +1,29 @@
-PADVALUE := 0xFF
-VERSION := 0
+# ROM Version
+VERSION := 0x01
+
+# 4 Character Game ID
 GAMEID := DTGM
+
+# ROM Title (14 chars max)
 TITLE := DMGTRIS
+
+# "Licensee" code (2 chars)
 LICENSEE := NR
-OLDLIC := 0x33
-MBC := 0x03
-SRAMSIZE := 0x02
-ROMNAME := out
-ROMEXT  := gb
+
+# Output options
+ROMNAME := DMGTRIS
+ROMEXT  := GBC
+
+# Extra assembler flags
+# Do not insert nop after halt
 ASFLAGS += -h
-LDFLAGS += -d
+# Do optimize ld to ldh
+ASFLAGS += -l
+
+# Extra linker flags
+# Tiny Rom
 LDFLAGS += -t
+
+# Extra fix flags
+# SEt as gbc compatible
+FIXFLAGS += -c
diff --git a/src/field.asm b/src/field.asm
index 443cd85..402cdda 100644
--- a/src/field.asm
+++ b/src/field.asm
@@ -143,6 +143,11 @@ FromShadowField:
 
     ; This routine will copy wField onto the screen.
 BlitField::
+    ; Hold on, are we on a gbc?
+    ld a, [wInitialA]
+    cp a, $11
+    jp z, GBCBlitField
+
     ; What to copy
     ld de, wField + 40
     ; Where to put it
diff --git a/src/gbc.asm b/src/gbc.asm
new file mode 100644
index 0000000..ab606d1
--- /dev/null
+++ b/src/gbc.asm
@@ -0,0 +1,558 @@
+; DMGTRIS
+; Copyright (C) 2023 - Randy Thiemann <randy.thiemann@gmail.com>
+
+; This program is free software: you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, either version 3 of the License, or
+; (at your option) any later version.
+
+; This program is distributed in the hope that it will be useful,
+; but WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+; GNU General Public License for more details.
+
+; You should have received a copy of the GNU General Public License
+; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+
+IF !DEF(GBC_ASM)
+DEF GBC_ASM EQU 1
+
+
+INCLUDE "globals.asm"
+
+DEF B0 EQU %0010000000000000
+DEF B1 EQU %0100000000000000
+DEF B2 EQU %0101000000000000
+DEF B3 EQU %0111110000000000
+DEF G0 EQU %0000000100000000
+DEF G1 EQU %0000001000000000
+DEF G2 EQU %0000001010000000
+DEF G3 EQU %0000001111100000
+DEF R0 EQU %0000000000001000
+DEF R1 EQU %0000000000010000
+DEF R2 EQU %0000000000010100
+DEF R3 EQU %0000000000011111
+
+
+SECTION "GBC Shadow Tilemap", WRAM0, ALIGN[8]
+wShadowTilemap:: ds 32*32
+
+SECTION "GBC Shadow Tile Attributes", WRAM0, ALIGN[8]
+wShadowTileAttrs:: ds 32*32
+
+SECTION "GBC Variables", WRAM0
+wOuterReps:: ds 1
+wInnerReps:: ds 1
+
+
+
+
+SECTION "GBC Functions", ROM0
+ToVRAM::
+    ; Bank 1
+    ld a, 1
+    ldh [rVBK], a
+    ld a, HIGH(wShadowTileAttrs)
+    ldh [rHDMA1], a
+    ld a, LOW(wShadowTileAttrs)
+    ldh [rHDMA2], a
+    ld a, HIGH($9800)
+    ldh [rHDMA3], a
+    ld a, LOW($9800)
+    ldh [rHDMA4], a
+    ld a, 39
+    ldh [rHDMA5], a
+
+
+    ; Bank 1
+    ld a, 0
+    ldh [rVBK], a
+    ld a, HIGH(wShadowTilemap)
+    ldh [rHDMA1], a
+    ld a, LOW(wShadowTilemap)
+    ldh [rHDMA2], a
+    ld a, HIGH($9800)
+    ldh [rHDMA3], a
+    ld a, LOW($9800)
+    ldh [rHDMA4], a
+    ld a, 39 | $80
+    ldh [rHDMA5], a
+
+GBCPalettes::
+    ld a, [wInitialA]
+    cp a, $11
+    ret nz
+    ld a, BCPSF_AUTOINC
+    ldh [rBCPS], a
+    ldh [rOCPS], a
+
+    ; Pal 0 (red, I)
+    ld bc, R3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 1 (green, Z)
+    ld bc, G3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, G2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, G1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, G0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 2 (purple, S)
+    ld bc, R3 | B3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R2 | B2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R1 | B1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R0 | B0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 3 (blue, J)
+    ld bc, B3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 4 (orange, L)
+    ld bc, R3 | G2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R2 | G1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R1 | G0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 5 (yellow, O)
+    ld bc, R3 | G3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R2 | G2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R1 | G1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, R0 | G0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Pal 6 (cyan, T)
+    ld bc, B3 | G3
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B2 | G2
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B1 | G1
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ld bc, B0 | G0
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ret
+
+
+GBCTitleInit::
+    ld a, [wInitialA]
+    cp a, $11
+    ret nz
+    ld a, BCPSF_AUTOINC | (7*8)
+    ldh [rBCPS], a
+    ldh [rOCPS], a
+
+    ; Pal 7 (grayscale, inverted)
+    ld bc, %0000000000000000
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0010000100001000
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0100001000010000
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0111111111111111
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Copy the tilemap to shadow.
+    ld de, $9800
+    ld hl, wShadowTilemap
+    ld bc, 32*32
+    call UnsafeMemCopy
+
+    ; Copy set attrs to pal 7 and copy to shadow.
+    ld a, 1
+    ldh [rVBK], a
+    ld d, $07
+    ld hl, $9800
+    ld bc, (32*32)
+    call UnsafeMemSet
+    ld de, $9800
+    ld hl, wShadowTileAttrs
+    ld bc, 32*32
+    call UnsafeMemCopy
+
+    ; Reset back to bank 0.
+    xor a, a
+    ldh [rVBK], a
+    ret
+
+
+GBCGameplayInit::
+    ld a, [wInitialA]
+    cp a, $11
+    ret nz
+    ld a, BCPSF_AUTOINC | (7*8)
+    ldh [rBCPS], a
+    ldh [rOCPS], a
+
+    ; Pal 7 (grayscale)
+    ld bc, %0111111111111111
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0100001000010000
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0010000100001000
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld bc, %0000000000000000
+    ld a, b
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+    ld a, c
+    ldh [rBCPD], a
+    ldh [rOCPD], a
+
+    ; Copy the tilemap to shadow.
+    ld de, $9800
+    ld hl, wShadowTilemap
+    ld bc, 32*32
+    call UnsafeMemCopy
+
+    ; Copy set attrs to pal 7 and copy to shadow.
+    ld a, 1
+    ldh [rVBK], a
+    ld d, $07
+    ld hl, $9800
+    ld bc, (32*32)
+    call UnsafeMemSet
+    ld de, $9800
+    ld hl, wShadowTileAttrs
+    ld bc, 32*32
+    call UnsafeMemCopy
+
+    ; Reset back to bank 0.
+    xor a, a
+    ldh [rVBK], a
+    ret
+
+
+GBCGameplayProcess::
+    ld a, [wInitialA]
+    cp a, $11
+    ret nz
+
+
+    ; What to copy
+    ld de, wField + 40
+    ; Where to put it
+    ld hl, wShadowTilemap + 1
+    ; How much to increment hl after each row
+    ld bc, 32-10
+
+    ; Blit me up daddy.
+    ld a, 20
+    ld [wOuterReps], a
+.outer1
+    ld a, 10
+    ld [wInnerReps], a
+.inner1
+    ld a, [de]
+    ld [hl+], a
+    inc de
+    ld a, [wInnerReps]
+    dec a
+    ld [wInnerReps], a
+    jr nz, .inner1
+
+    add hl, bc
+    ld a, [wOuterReps]
+    dec a
+    ld [wOuterReps], a
+    jr nz, .outer1
+
+
+    ; What to copy
+    ld de, wField + 40
+    ; Where to put it
+    ld hl, wShadowTileAttrs + 1
+    ; How much to increment hl after each row
+    ld bc, 32-10
+
+    ; Blit me up daddy.
+    ld a, 20
+    ld [wOuterReps], a
+.outer2
+    ld a, 10
+    ld [wInnerReps], a
+.inner2
+    ld a, [de]
+    cp a, 10
+    jr c, .empty
+    cp a, 10 + (1*7)
+    jr c, .sub10
+    cp a, 10 + (2*7)
+    jr c, .sub17
+    cp a, 10 + (3*7)
+    jr c, .sub24
+    cp a, 10 + (4*7)
+    jr c, .sub31
+    cp a, 10 + (5*7)
+    jr c, .sub38
+    cp a, 10 + (6*7)
+    jr c, .sub45
+    cp a, 10 + (7*7)
+    jr c, .sub52
+    cp a, 10 + (8*7)
+    jr c, .sub59
+.empty
+    ld a, $07
+    jr .done
+.sub59
+    sub a, 7
+.sub52
+    sub a, 7
+.sub45
+    sub a, 7
+.sub38
+    sub a, 7
+.sub31
+    sub a, 7
+.sub24
+    sub a, 7
+.sub17
+    sub a, 7
+.sub10
+    sub a, 10
+.done
+    ld [hl+], a
+    inc de
+    ld a, [wInnerReps]
+    dec a
+    ld [wInnerReps], a
+    jr nz, .inner2
+
+    add hl, bc
+    ld a, [wOuterReps]
+    dec a
+    ld [wOuterReps], a
+    jr nz, .outer2
+
+
+    ret
+
+
+
+GBCBlitField::
+    call ToVRAM
+    jp EventLoop
+
+
+ENDC
diff --git a/src/main.asm b/src/main.asm
index 2b2cd2b..4e60602 100644
--- a/src/main.asm
+++ b/src/main.asm
@@ -86,6 +86,16 @@ Main::
     ; Set up stack
     ld sp, wStackEnd-1
 
+    ; GBC? Double speed mode and set up palettes.
+    ld a, [wInitialA]
+    cp a, $11
+    jr nz, .notgbc
+    ld a, KEY1F_PREPARE
+    ldh [rKEY1], a
+    stop
+    call GBCPalettes
+.notgbc
+
     ; We use a single set of tiles for the entire game, so we copy it at the start.
     ld de, Tiles
     ld hl, _VRAM
diff --git a/src/sprites.asm b/src/sprites.asm
index db49fa6..52e048d 100644
--- a/src/sprites.asm
+++ b/src/sprites.asm
@@ -101,6 +101,12 @@ ClearOAM::
 SECTION "Domain Specific Functions", ROM0
 ; Index of next piece in A.
 ApplyNext::
+    ; Correct color
+    ld [wSPRNext1+3], a
+    ld [wSPRNext2+3], a
+    ld [wSPRNext3+3], a
+    ld [wSPRNext4+3], a
+
     ; Correct tile
     add a, TILE_PIECE_0
     ld [wSPRNext1+2], a
@@ -167,6 +173,12 @@ ApplyHold::
     ret
 
 .doApplyHold
+    ; Correct color
+    ld [wSPRHold1+3], a
+    ld [wSPRHold2+3], a
+    ld [wSPRHold3+3], a
+    ld [wSPRHold4+3], a
+
     ; Correct tile
     add a, TILE_PIECE_0
     ld [wSPRHold1+2], a
@@ -277,7 +289,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -289,7 +301,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -301,7 +313,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -313,7 +325,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -325,7 +337,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -336,7 +348,7 @@ SetNumberSpritePositions::
     ld [hl], a
     inc hl
     inc hl
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
 
     ld a, LEVEL_BASE_X
@@ -347,7 +359,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -359,7 +371,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -371,7 +383,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -382,7 +394,7 @@ SetNumberSpritePositions::
     ld [hl], a
     inc hl
     inc hl
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
 
     ld a, LEVEL_BASE_X
@@ -393,7 +405,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -405,7 +417,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -417,7 +429,7 @@ SetNumberSpritePositions::
     inc hl
     inc hl
     ld b, a
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ld a, b
     add a, 8
@@ -428,7 +440,7 @@ SetNumberSpritePositions::
     ld [hl], a
     inc hl
     inc hl
-    ld a, OAMF_PAL1
+    ld a, OAMF_PAL1 | $07
     ld [hl], a
     ret
 
diff --git a/src/state_gameplay.asm b/src/state_gameplay.asm
index a8a82fd..c7b527d 100644
--- a/src/state_gameplay.asm
+++ b/src/state_gameplay.asm
@@ -110,6 +110,9 @@ SwitchToGameplay::
     ld a, LEADY_TIME
     ldh [hModeCounter], a
 
+    ; GBC init
+    call GBCGameplayInit
+
     ; Install the event loop handlers.
     ld a, 1
     ldh [hGameState], a
@@ -526,6 +529,8 @@ drawStaticInfo:
     ld de, hNLevel
     call ApplyNumbers
 
+    call GBCGameplayProcess
+
     jp EventLoopPostHandler
 
 
diff --git a/src/state_title.asm b/src/state_title.asm
index a713d86..980a81a 100644
--- a/src/state_title.asm
+++ b/src/state_title.asm
@@ -78,6 +78,9 @@ SwitchToTitle::
     set_obj0_palette
     set_obj1_palette
 
+    ; GBC init
+    call GBCTitleInit
+
     ; Install the event loop handlers.
     ld a, 0
     ldh [hGameState], a