Just for fun

src/dmgfx.asm

@@ -0,0 +1,89 @@
+; 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(DMGFX_ASM)
+DEF DMGFX_ASM EQU 1
+
+
+INCLUDE "globals.asm"
+
+
+SECTION "DMG Intro Effect", ROM0
+DoDMGEffect::
+    ld a, [wInitialA]
+    cp a, $11
+    ret z
+
+    ; Yeet the logo
+    ld c, 10
+.loop0
+    wait_vblank
+    ldh a, [rSCY]
+    dec a
+    ldh [rSCY], a
+    wait_vblank_end
+    dec c
+    jr nz, .loop0
+
+    ld c, 45
+.loop1
+    wait_vblank
+    ldh a, [rSCY]
+    inc a
+    inc a
+    ldh [rSCY], a
+    wait_vblank_end
+    dec c
+    jr nz, .loop1
+
+    ; Fade
+    wait_vblank
+    ld a, PALETTE_MONO_2
+    ldh [rBGP], a
+
+    ld c, 20
+.loop2
+    wait_vblank
+    wait_vblank_end
+    dec c
+    jr nz, .loop2
+
+    wait_vblank
+    ld a, PALETTE_MONO_1
+    ldh [rBGP], a
+
+    ld c, 20
+.loop3
+    wait_vblank
+    wait_vblank_end
+    dec c
+    jr nz, .loop3
+
+    wait_vblank
+    ld a, PALETTE_MONO_0
+    ldh [rBGP], a
+
+    ld c, 20
+.loop4
+    wait_vblank
+    wait_vblank_end
+    dec c
+    jr nz, .loop4
+    ret
+
+
+ENDC

src/include/globals.asm

@@ -26,9 +26,9 @@ INCLUDE "structs.asm"
 ; Waits for PPU mode to be 0 or 1.
 ; We don't wait for 2 because it's super short and impractical to do much of anything in.
 MACRO wait_vram
-    ld hl, rSTAT
 .wvr\@
-    bit STATB_BUSY, [hl]
+    ldh a, [rSTAT]
+    bit STATB_BUSY, a
     jr nz, .wvr\@
 ENDM
 

src/main.asm

@@ -68,13 +68,20 @@ Main::
     ld a, l
     ld [wInitialL], a
 
-    ; Turn off LCD during initialization.
+    ; Let the DMG have some fun with the initial screen.
+    call DoDMGEffect
+
+    ; Turn off LCD during initialization, but not on DMG.
+    ld a, [wInitialA]
+    cp a, $11
+    jr nz, :+
+
     wait_vram
     xor a, a
     ldh [rLCDC], a
 
     ; Set up stack
-    ld sp, wStackEnd-1
+:   ld sp, wStackEnd-1
 
     ; GBC? Double speed mode and set up palettes.
     ld a, [wInitialA]
@@ -96,7 +103,7 @@ Main::
     ld de, Tiles
     ld hl, _VRAM
     ld bc, TilesEnd - Tiles
-    call UnsafeMemCopy
+    call SafeMemCopy
 
     ; Clear OAM.
     call ClearOAM
@@ -111,7 +118,11 @@ Main::
     call SFXInit
 
     ; Set up the interrupt handlers.
-    call InitializeLCDCInterrupt
+    ld a, [wInitialA]
+    cp a, $11
+    jr nz, :+
+    wait_vblank
+:   call InitializeLCDCInterrupt
 
     ; Switch to gameplay state.
     call SwitchToTitle

src/memory.asm

@@ -57,5 +57,15 @@ UnsafeMemSet::
     jr nz, UnsafeMemSet
     ret
 
+SafeMemSet::
+    wait_vram
+    ld [hl], d
+    inc hl
+    dec bc
+    ld a, b
+    or a, c
+    jr nz, SafeMemSet
+    ret
+
 
 ENDC

src/sprites.asm

@@ -85,11 +85,11 @@ ClearOAM::
     ld hl, _OAMRAM
     ld bc, $9F
     ld d, 0
-    call UnsafeMemSet
+    call SafeMemSet
     ld hl, wShadowOAM
     ld bc, $9F
     ld d, 0
-    call UnsafeMemSet
+    call SafeMemSet
     ret