From 2ab9a1f3a04cc7f9fa1dea9d4c85d619a6804144 Mon Sep 17 00:00:00 2001
From: Louis Pearson <opensource@louispearson.work>
Date: Thu, 18 Apr 2024 01:48:36 -0600
Subject: [PATCH] feat: 3d movement

Needs gravity, shadow
---
 build.zig |   1 +
 main.asm  | 199 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 184 insertions(+), 16 deletions(-)

diff --git a/build.zig b/build.zig
index ebf0782..0214274 100644
--- a/build.zig
+++ b/build.zig
@@ -10,6 +10,7 @@ pub fn build(b: *std.Build) !void {
     });
 
     const assemble = b.addRunArtifact(rgbds.artifact("rgbasm"));
+    assemble.addArg("-H");
     assemble.addArg("-L");
     assemble.addArg("-o");
     const main_obj = assemble.addOutputFileArg("main.o");
diff --git a/main.asm b/main.asm
index 6c937a2..268eff3 100644
--- a/main.asm
+++ b/main.asm
@@ -7,7 +7,7 @@ SECTION "Header", ROM0[$100]
 
 	ds $150 - @, 0 ; Make room for the header
 
-SECTION "Init", ROM0
+SECTION "Main", ROM0
 Init:
 	; Shut down audio circuitry
 	ld a, 0
@@ -46,11 +46,23 @@ WaitVBlank:
 	ld a, 8
 	ld [hl], a
 
-	ld hl, wMetaspritePosition
+	ld hl, wMetaspritePosition.x
 	ld a, 0
-	ld [wMetaspritePosition], a
+	ld [wMetaspritePosition.x], a
 	ld a, $80
-	ld [wMetaspritePosition + 1], a
+	ld [wMetaspritePosition.x + 1], a
+
+	ld hl, wMetaspritePosition.y
+	ld a, 0
+	ld [wMetaspritePosition.y], a
+	ld a, $80
+	ld [wMetaspritePosition.y + 1], a
+
+	ld hl, wMetaspritePosition.z
+	ld a, 0
+	ld [wMetaspritePosition.z], a 
+	ld a, 0
+	ld [wMetaspritePosition.z + 1], a 
 
 	; Copy the tile data
 	ld de, Tiles
@@ -85,6 +97,103 @@ WaitVBlank:
 
 Main:
 	call ResetShadowOAM
+	call UpdateJoypadState
+
+	ld a, [wJoypadState]
+	bit PADB_LEFT, a
+	jr nz, .leftend
+
+	ld a, [wMetaspritePosition.x]
+	add a, 16
+	ld b, a
+	ld [wMetaspritePosition.x], a
+	ld a, [wMetaspritePosition.x+1]
+	adc 0
+	ld c, a
+	ld [wMetaspritePosition.x+1], a
+.leftend:
+
+	ld a, [wJoypadState]
+	bit PADB_RIGHT, a
+	jr nz, .rightend
+
+	ld a, [wMetaspritePosition.x]
+	sub a, 16
+	ld b, a
+	ld [wMetaspritePosition.x], a
+	ld a, [wMetaspritePosition.x+1]
+	sbc 0
+	ld c, a
+	ld [wMetaspritePosition.x+1], a
+.rightend:
+
+	ld a, [wJoypadState]
+	bit PADB_UP, a
+	jr nz, .upend
+
+	ld a, [wMetaspritePosition.y]
+	add a, 16
+	ld b, a
+	ld [wMetaspritePosition.y], a
+	ld a, [wMetaspritePosition.y+1]
+	adc 0
+	ld c, a
+	ld [wMetaspritePosition.y+1], a
+.upend:
+ 
+	ld a, [wJoypadState]
+	bit PADB_DOWN, a
+	jr nz, .downend
+
+	ld a, [wMetaspritePosition.y]
+	sub a, 16
+	ld b, a
+	ld [wMetaspritePosition.y], a
+	ld a, [wMetaspritePosition.y+1]
+	sbc 0
+	ld c, a
+	ld [wMetaspritePosition.y+1], a
+.downend: 
+
+	ld a, [wJoypadState]
+	bit PADB_A, a
+	jr nz, .jumpend
+
+	ld a, [wMetaspritePosition.z]
+	add a, 16
+	ld b, a
+	ld [wMetaspritePosition.z], a
+	ld a, [wMetaspritePosition.z+1]
+	adc 0
+	ld c, a
+	ld [wMetaspritePosition.z+1], a
+
+.jumpend
+
+	ld a, [wJoypadState]
+	bit PADB_B, a
+	jr nz, .fallend
+
+	ld a, [wMetaspritePosition.z + 1]
+	cp 0
+	jr nz, .fall
+	ld a, [wMetaspritePosition.z]
+	cp 16
+	jr nc, .fall
+	ld a, 0
+	ld [wMetaspritePosition.z], a
+	jr .fallend
+
+.fall
+	ld a, [wMetaspritePosition.z]
+	sub a, 16
+	ld b, a
+	ld [wMetaspritePosition.z], a
+	ld a, [wMetaspritePosition.z+1]
+	sbc 0
+	ld c, a
+	ld [wMetaspritePosition.z+1], a  
+.fallend
 
 	ld de, $0100
 	ld c, 8
@@ -94,11 +203,24 @@ Main:
 	ld hl, wSimplePosition
 	inc [hl]
 
-	ld bc, (96.0 >> 12) & $FFFF
-	ld a, [wMetaspritePosition]
+	; load de
+	ld a, [wMetaspritePosition.x]
 	ld e, a
-	ld a, [wMetaspritePosition + 1]
+	ld a, [wMetaspritePosition.x + 1]
 	ld d, a
+
+	; load bc
+	ld a, [wMetaspritePosition.z]
+	ld c, a
+	ld a, [wMetaspritePosition.y]
+	sub a, c
+	ld c, a
+	ld a, [wMetaspritePosition.z + 1]
+	ld b, a
+	ld a, [wMetaspritePosition.y + 1]
+	sbc a, b
+	ld b, a
+
 	ld hl, CatMetasprite
 	call RenderMetasprite
 
@@ -125,6 +247,40 @@ Memcopy::
 	jr nz, .loop
 	ret
 
+UpdateJoypadState::
+	ld hl, rP1
+	ld [hl], P1F_GET_BTN
+	; Read button state twice to ensure we get the proper state
+	ld a, [hl]
+	ld a, [hl]
+	ld [hl], P1F_GET_DPAD
+	cpl ; Inputs are active low - invert so it makes more sense
+	and PADF_A | PADF_B | PADF_SELECT | PADF_START
+	ld c, a ; Store lower 4 button bits in c
+
+	; On real hardware, rP1 needs to be read 8 times to ensure proper state is read
+	ld b, 8
+.dpadDebounceLoop:
+	ld a, [hl]
+	dec b
+	jr nz, .dpadDebounceLoop
+	ld [hl], P1F_GET_NONE ; Disable joypad inputs
+
+	swap a ; Swap the nibbles to store dpad in upper 4 bits
+	cpl    ; invert the bits
+	and PADF_RIGHT | PADF_LEFT | PADF_UP | PADF_DOWN
+	or c
+	ld c, a
+
+	; Compare with previously stored state
+	ld hl, wJoypadState
+	xor [hl]
+	and c
+	ld [wJoypadPressed], a
+	ld a, c
+	ld [wJoypadState], a
+	ret
+
 
 SECTION "VBlank Interrupt", ROM0[$0040]
 VBlankInterrupt:
@@ -265,25 +421,36 @@ TilemapEnd:
 
 SECTION "Graphics", ROM0
 GfxCat:
-  INCBIN "cat.2bpp"
+	INCBIN "cat.2bpp"
 .end::
 
 CatMetasprite:
-  db 16, 8, 0, 0
-  db 12, 16, 0, 0
-  db 20, 20, 0, 0
-  db 24, 12, 0, 0
-  db 128
+	db 16, 8, 0, 0
+	db 12, 16, 0, 0
+	db 20, 20, 0, 0
+	db 24, 12, 0, 0
+	db 128
 
 SECTION "Position Vars", WRAM0
 ; 8-bit X position
 wSimplePosition:
-  ds 1
+	ds 1
 
 ; Q12.4 fixed-point X posiition
 wMetaspritePosition:
-  dw
+.x:
+	dw
+.y:
+	dw
+.z:
+	dw
 
 ; Q4.4 fixed-point velocity
 wMetaspriteVelocity::
-  db
+	db
+
+SECTION "Joypad Vars", WRAM0
+wJoypadState:
+	ds 1
+wJoypadPressed:
+	ds 1