diff --git a/inc/oam.inc b/inc/oam.inc
new file mode 100644
index 0000000..59633e2
--- /dev/null
+++ b/inc/oam.inc
@@ -0,0 +1,47 @@
+INCLUDE "hardware.inc"
+
+; The address of an internal OAM entry
+; @param \1 16-bit register
+; @param \2 OAM index
+; @param \3 offset
+MACRO ld_OAM
+    ld \1, _OAM + \2 * sizeof_OAM_ATTRS + \3
+ENDM
+
+; The address of an internal OAM entry's Y coordinate
+MACRO ld_OAM_y
+    ld_OAM \1, \2, 0
+ENDM
+
+; The address of an internal OAM entry's X coordinate
+MACRO ld_OAM_x
+    ld_OAM \1, \2, 1
+ENDM
+
+; The address of an internal OAM entry's tile index
+MACRO ld_OAM_tile
+    ld_OAM \1, \2, 2
+ENDM
+
+; The address of an internal OAM entry's attributes
+MACRO ld_OAM_attr
+    ld_OAM \1, \2, 3
+ENDM
+
+; Set an entry in the internal OAM (copied on next DMA)
+; @param \1 OAM index
+; @param \2 X coordinate
+; @param \3 Y coordinate
+; @param \4 Tile index
+; @param \5 Attributes
+MACRO OAM_set
+    ld_OAM_y hl, \1
+    ld a, \3
+    ld [hli], a
+    ld a, \2
+    ld [hli], a
+    ld a, \4
+    ld [hli], a
+    ld a, \5
+    ld [hl], a
+ENDM
diff --git a/src/oam.s b/src/oam.s
index 74da1b8..34f8d39 100644
--- a/src/oam.s
+++ b/src/oam.s
@@ -2,7 +2,7 @@ INCLUDE "hardware.inc"
 
 SECTION "OAM Mirror", WRAM0, ALIGN[8]
 
-_OAM:: ds 40 * 4
+_OAM:: ds OAM_COUNT * sizeof_OAM_ATTRS
 _OAM_end:
 
 SECTION "OAM DMA routine", ROM0
diff --git a/src/player.s b/src/player.s
index a57eb7f..b8d3578 100644
--- a/src/player.s
+++ b/src/player.s
@@ -1,5 +1,6 @@
 INCLUDE "hardware.inc"
 INCLUDE "input.inc"
+INCLUDE "oam.inc"
 
 Section "Player Data", WRAM0
 
@@ -11,7 +12,8 @@ Section "Player Code", ROM0
 spriteData:
     INCBIN "png/sprite/player.2bpp"
 
-DEF SPRITE_IDX EQU 32
+DEF SPRITE_OAM_IDX EQU 0
+DEF SPRITE_IDX EQU 32 ; tile index, rename later
 DEF SPRITE_WIDTH EQU 2
 DEF SPRITE_HEIGHT EQU 2
 
@@ -25,46 +27,10 @@ Player_Init::
     ld d, 16 * (SPRITE_WIDTH * SPRITE_HEIGHT)
     call memcpy
 
-    ; top left
-    ld hl, _OAM
-    ld a, 144-8-8
-    ld [hli], a
-    ld a, 8
-    ld [hli], a
-    ld a, SPRITE_IDX
-    ld [hli], a
-    xor a
-    ld [hli], a
-
-    ; top right
-    ld a, 144-8-8
-    ld [hli], a
-    ld a, 8 + 8
-    ld [hli], a
-    ld a, SPRITE_IDX + 1
-    ld [hli], a
-    xor a
-    ld [hli], a
-
-    ; bottom left
-    ld a, 144-8
-    ld [hli], a
-    ld a, 8
-    ld [hli], a
-    ld a, SPRITE_IDX + 2
-    ld [hli], a
-    xor a
-    ld [hli], a
-
-    ; bottom right
-    ld a, 144-8
-    ld [hli], a
-    ld a, 8 + 8
-    ld [hli], a
-    ld a, SPRITE_IDX + 3
-    ld [hli], a
-    xor a
-    ld [hli], a
+    OAM_set SPRITE_OAM_IDX + 0, 8, 144-8-8, SPRITE_IDX, 0
+    OAM_set SPRITE_OAM_IDX + 1, 16, 144-8-8, SPRITE_IDX + 1, 0
+    OAM_set SPRITE_OAM_IDX + 2, 8, 144-8, SPRITE_IDX + 2, 0
+    OAM_set SPRITE_OAM_IDX + 3, 16, 144-8, SPRITE_IDX + 3, 0
 
     ld bc, _OAMRAM
     ld hl, _OAM
@@ -79,7 +45,7 @@ Player_Update::
     ld a, [hl]
     and %1
     cp %1
-    jr nz, .done
+    ret nz
 
     ld hl, keys
     ld b, [hl]
@@ -90,17 +56,40 @@ Player_Update::
     jr z, .left
 
     ; check for right boundary
-    ld hl, _OAM + 1
+    ld_OAM_x hl, SPRITE_OAM_IDX + 1
     ld a, [hl]
-    cp 160 - 8
-    jr nc, .done
+    cp SCRN_X
+    jr nc, .left
+
+    ; TODO: check collision
+    call move_right
+
+.left:
+    ; check for left button
+    ld a, b
+    and BTN_LEFT
+    ret z
+
+    ; check for left boundary
+    ld_OAM_x hl, SPRITE_OAM_IDX
+    ld a, [hl]
+    cp 9
+    ret c
+
+    ; TODO: check collision
+    call move_left
+
+    ret
+
+move_right:
+    ld_OAM_x hl, SPRITE_OAM_IDX
 
     ; update top left sprite
     inc [hl]
     inc hl
     ld [hl], SPRITE_IDX
     inc hl
-    res 5, [hl]
+    res OAMB_XFLIP, [hl]
 
     ; update top right sprite
     inc hl
@@ -109,7 +98,7 @@ Player_Update::
     inc hl
     ld [hl], SPRITE_IDX + 1
     inc hl
-    res 5, [hl]
+    res OAMB_XFLIP, [hl]
 
     ; update bottom left sprite
     inc hl
@@ -118,7 +107,7 @@ Player_Update::
     inc hl
     ld [hl], SPRITE_IDX + 2
     inc hl
-    res 5, [hl]
+    res OAMB_XFLIP, [hl]
 
     ; update bottom right sprite
     inc hl
@@ -127,53 +116,45 @@ Player_Update::
     inc hl
     ld [hl], SPRITE_IDX + 3
     inc hl
-    res 5, [hl]
+    res OAMB_XFLIP, [hl]
 
-.left:
-    ; check for left button
-    ld a, b
-    and BTN_LEFT
-    jr z, .done
+    ret
 
-    ; check for left boundary
-    ld hl, _OAM + 1
-    ld a, [hl]
-    cp 9
-    jr c, .done
+move_left:
+    ld_OAM_x hl, SPRITE_OAM_IDX
 
-    ; update top left sprite
+    ; top left
     dec [hl]
     inc hl
     ld [hl], SPRITE_IDX + 1
     inc hl
-    set 5, [hl]
+    set OAMB_XFLIP, [hl]
 
-    ; update top right sprite
+    ; top right
     inc hl
     inc hl
     dec [hl]
     inc hl
     ld [hl], SPRITE_IDX
     inc hl
-    set 5, [hl]
+    set OAMB_XFLIP, [hl]
 
-    ; update bottom left sprite
+    ; bottom left
     inc hl
     inc hl
     dec [hl]
     inc hl
     ld [hl], SPRITE_IDX + 3
     inc hl
-    set 5, [hl]
+    set OAMB_XFLIP, [hl]
 
-    ; update bottom right sprite
+    ; bottom right
     inc hl
     inc hl
     dec [hl]
     inc hl
     ld [hl], SPRITE_IDX + 2
     inc hl
-    set 5, [hl]
+    set OAMB_XFLIP, [hl]
 
-.done:
     ret