Dump MoveBallPosition routine.

2 files changed, 84 insertions, 13 deletions

diff --git a/main.asm b/main.asm
index a67768b..97b8893 100755
--- a/main.asm
+++ b/main.asm
@@ -2797,7 +2797,53 @@ Func_208c: ; 0x208c
     scf
     ret
 
-INCBIN "baserom.gbc",$20ab,$30db - $20ab
+INCBIN "baserom.gbc",$20ab,$219c - $20ab
+
+MoveBallPosition: ; 0x219c
+; Updates the ball's position according to its velocity
+    ld a, [wBallXPos]
+    ld [wPreviousBallXPos], a
+    ld a, [wBallXPos + 1]
+    ld [wPreviousBallXPos + 1], a
+    ld a, [wBallYPos]
+    ld [wPreviousBallYPos], a
+    ld a, [wBallYPos + 1]
+    ld [wPreviousBallYPos + 1], a
+    ld de, wBallXVelocity + 1
+    ld hl, wBallXPos
+    call AddVelocityToPosition
+    ld de, wBallYVelocity + 1
+    ld hl, wBallYPos
+    ; fall through
+
+AddVelocityToPosition: ; 0x21c3
+    ld a, [de]
+    bit 7, a
+    jr nz, .asm_21d1
+    cp $5
+    jr c, .asm_21da
+    ld bc, $04ff
+    jr .asm_21de
+.asm_21d1
+    cp $fc
+    jr nc, .asm_21da
+    ld bc, $fb01
+    jr .asm_21de
+.asm_21da
+    ld b, a
+    dec de
+    ld a, [de]
+    ld c, a
+.asm_21de
+    ld a, [hl]
+    add c
+    ld [hli], a
+    ld a, [hl]
+    adc b
+    ld [hl], a
+    ret
+
+INCBIN "baserom.gbc",$21e5,$30db - $21e5
 
 Func_30db: ; 0x30db
     ld a, $86
@@ -7158,12 +7204,12 @@ Func_17e81: ; 0x17e81
     ld a, [wBallRotation]
     add [hl]
     ld [wBallRotation], a
-    ld a, [wBallXPos]
+    ld a, [wBallXPos + 1]
     inc a
     ld hl, hBoardXShift
     sub [hl]
     ld b, a
-    ld a, [wBallYPos]
+    ld a, [wBallYPos + 1]
     inc a
     sub $10
     ld hl, hBoardYShift
@@ -7205,9 +7251,9 @@ Func_17e81: ; 0x17e81
     and $7
     add $0
     call LoadOAMData
-    ld a, [wBallXPos]
+    ld a, [wBallXPos + 1]
     ld [$d4c5], a
-    ld a, [wBallYPos]
+    ld a, [wBallYPos + 1]
     ld [$d4c6], a
     ld a, [wBallRotation]
     ld [$d4c7], a
diff --git a/wram.asm b/wram.asm
index 2adfe52..d61be27 100755
--- a/wram.asm
+++ b/wram.asm
@@ -13,18 +13,43 @@ wOAMBuffer:: ; d000
     ; buffer for OAM data. Copied to OAM by DMA
     ds 4 * 40
 
-    ds $414
+    ds $413
 
-wBallXPos:: ; 0xd4b4
+wBallXPos:: ; 0xd4b3
 ; x coordinate of the center of the pokeball
-    ds 1
-    ds 1
-wBallYPos:: ; 0xd4b6
+; little-endian word
+; Most-significant byte is the pixel, and least-significant byte is fraction of a pixel
+    ds 2
+
+wBallYPos:: ; 0xd4b5
 ; y coordinate of the center of the pokeball
-    ds 1
-    ds 1
+; little-endian word
+; Most-significant byte is the pixel, and least-significant byte is fraction of a pixel
+    ds 2
+
+wPreviousBallXPos:: ; 0xd4b7
+; x coordinate of the center of the pokeball in the previous frame
+; little-endian word
+; Most-significant byte is the pixel, and least-significant byte is fraction of a pixel
+    ds 2
+
+wPreviousBallYPos:: ; 0xd4b9
+; y coordinate of the center of the pokeball in the previous frame
+; little-endian word
+; Most-significant byte is the pixel, and least-significant byte is fraction of a pixel
+    ds 2
+
+wBallXVelocity:: ; 0xd4bb
+; little-endian word
+; This is added to wBallXPos every frame.
+    ds 2
+
+wBallYVelocity:: ; 0xd4bd
+; little-endian word
+; This is added to wBallYPos every frame.
+    ds 2
 
-    ds $b
+    ds 4
 
 wBallSpin:: ; 0xd4c3
     ds 1