From 9ff2033e936689135210989a5fee057a4a13527e Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Thu, 13 Mar 2025 22:52:49 +0100
Subject: Add a title and a main screens
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This commit adds the skeleton for having a title and a main screen. For
now the title menu doesn't do much, as the selection is simply ignored,
but at least it already knows how to cycle between these two states.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 src/jetpac.s | 113 ++++++++++++++++++++++++++++++-----------------------------
 1 file changed, 58 insertions(+), 55 deletions(-)

(limited to 'src/jetpac.s')

diff --git a/src/jetpac.s b/src/jetpac.s
index 2f273a3..8acbb4e 100644
--- a/src/jetpac.s
+++ b/src/jetpac.s
@@ -5,28 +5,74 @@
 
 .segment "CODE"
 
+;; NOTE: automatically generated by the build system.
+.include "../config/generated.s"
+
 .include "../include/apu.s"
 .include "../include/oam.s"
 .include "../include/ppu.s"
+.include "../include/asm.s"
+.include "../include/joypad.s"
 .include "../include/globals.s"
+
+.include "assets.s"
+.include "driver.s"
+.include "title.s"
 .include "vectors.s"
 
 .proc main
-    jsr init_palettes
-    jsr init_nametables
+    ;; Disable the PPU.
+    lda #0
+    sta PPU::MASK
+
+    ;; Initialize the assets for the game.
+    jsr Assets::init
+
+    ;; We shadow the PPU control register in memory. Depending on the `make`
+    ;; target we might need to switch directly to the main game. Otherwise we go
+    ;; into the title as expected.
+    .ifdef PARTIAL
+        jsr Driver::switch
+
+        lda PPU::zp_control
+        sta PPU::CONTROL
+    .else
+        jsr Title::init
+
+        lda #%10001000
+        sta PPU::zp_control
+        sta PPU::CONTROL
+    .endif
 
-;;; TODO
     cli
-    lda #%10110000
-    sta $2000
+
+    ;; Enable back the PPU
     lda #%00011110
-    sta $2001
+    sta PPU::MASK
 
 @main_game_loop:
-    ;;;
-    ;; TODO
-    ;;;
+    READ_JOYPAD1
+
+    lda Globals::zp_flags
+    and #%00000011
+    beq @title_screen
+    cmp #1
+    beq @game_screen
+    jmp @over
 
+@title_screen:
+    jsr Title::update
+    beq @set_flags
+
+    ;; Start was pressed by the player, switch to the main game.
+    jsr Driver::switch
+    jmp @set_flags
+
+@game_screen:
+    jsr Driver::update
+    ;; NOTE: fallthrough
+
+@set_flags:
     lda #%10000000
     ora Globals::zp_flags
     sta Globals::zp_flags
@@ -36,51 +82,8 @@
 
     ;; Rendering is done, we can perform another iteration of the loop!
     jmp @main_game_loop
-.endproc
 
-;; Copies all the palettes for our game into the proper PPU address.
-.proc init_palettes
-    lda #$3F
-    sta PPU::ADDRESS
-    lda #$00
-    sta PPU::ADDRESS
-
-    ldx #0
-@load_palettes_loop:
-    lda palettes, x
-    sta PPU::DATA
-    inx
-    cpx #$20
-    bne @load_palettes_loop
-    rts
-palettes:
-    ;; Background
-    ;; 0: score
-    .byte $0F, $30, $2C, $28
-    ;; 1: floating platforms
-    .byte $0F, $2C, $30, $2A
-    ;; 2: ground
-    .byte $0F, $28, $14, $28
-    ;; 3: ship
-    .byte $0F, $16, $30, $00
-
-    ;; TODO: fuel tank needs color $24
-    ;; Foreground
-    ;; 0: player & ship
-    .byte $0F, $16, $10, $30
-    ;; 1: enemy 1 & bonuses
-    .byte $0F, $16, $2C, $2A
-    ;; 2: enemy 2, fuel & bonuses
-    .byte $0F, $16, $14, $28
-    ;; 3: SUSE easter egg
-    .byte $0F, $16, $00, $2B
+@over:
+    ;; TODO: allow to start over, reset flags, control register, etc.
+    jmp @over
 .endproc
-
-.proc init_nametables
-    ;; TODO
-    rts
-.endproc
-
-
-.segment "CHARS"
-    .incbin "../assets/jetpac.chr"
-- 
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