From 2627b459d9a19ce7f1b7f3a359dca3b30b66b34e Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Wed, 12 Mar 2025 22:38:12 +0100
Subject: Start with a skeleton for the project
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Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 src/jetpac.s  |  86 +++++++++++++++++++++++++++++++++++++++++++++
 src/vectors.s | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 195 insertions(+)
 create mode 100644 src/jetpac.s
 create mode 100644 src/vectors.s

(limited to 'src')

diff --git a/src/jetpac.s b/src/jetpac.s
new file mode 100644
index 0000000..2f273a3
--- /dev/null
+++ b/src/jetpac.s
@@ -0,0 +1,86 @@
+.segment "HEADER"
+    .byte 'N', 'E', 'S', $1A
+    .byte $02, $01
+    .res $0A, $00
+
+.segment "CODE"
+
+.include "../include/apu.s"
+.include "../include/oam.s"
+.include "../include/ppu.s"
+.include "../include/globals.s"
+.include "vectors.s"
+
+.proc main
+    jsr init_palettes
+    jsr init_nametables
+
+;;; TODO
+    cli
+    lda #%10110000
+    sta $2000
+    lda #%00011110
+    sta $2001
+
+@main_game_loop:
+    ;;;
+    ;; TODO
+    ;;;
+
+    lda #%10000000
+    ora Globals::zp_flags
+    sta Globals::zp_flags
+@wait_for_render:
+    bit Globals::zp_flags
+    bmi @wait_for_render
+
+    ;; 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
+.endproc
+
+.proc init_nametables
+    ;; TODO
+    rts
+.endproc
+
+
+.segment "CHARS"
+    .incbin "../assets/jetpac.chr"
diff --git a/src/vectors.s b/src/vectors.s
new file mode 100644
index 0000000..2edc6a6
--- /dev/null
+++ b/src/vectors.s
@@ -0,0 +1,109 @@
+.segment "VECTORS"
+    .addr nmi, reset, irq
+
+.segment "CODE"
+
+;; Pretty standard reset function, nothing crazy.
+.proc reset
+    sei
+    cld
+
+    ldx #$40
+    stx APU::FRAME_COUNTER
+
+    ldx #$FF
+    txs
+
+    inx
+    stx PPU::CONTROL
+    stx PPU::MASK
+    stx APU::DMC
+
+@vblankwait1:
+    bit PPU::STATUS
+    bpl @vblankwait1
+
+    ldx #0
+    lda #0
+@ram_reset_loop:
+    sta $000, x
+    sta $100, x
+    sta $300, x
+    sta $400, x
+    sta $500, x
+    sta $600, x
+    sta $700, x
+    inx
+    bne @ram_reset_loop
+
+    lda #$EF
+@sprite_reset_loop:
+    sta $200, x
+    inx
+    bne @sprite_reset_loop
+
+    lda #$00
+    sta OAM::ADDRESS
+    lda #$02
+    sta OAM::DMA
+
+@vblankwait2:
+    bit PPU::STATUS
+    bpl @vblankwait2
+
+    lda #$3F
+    sta PPU::ADDRESS
+    lda #$00
+    sta PPU::ADDRESS
+
+    lda #$0F
+    ldx #$20
+@palettes_reset_loop:
+    sta PPU::DATA
+    dex
+    bne @palettes_reset_loop
+
+    jmp main
+.endproc
+
+.proc nmi
+    ;; Should we skip it?
+    bit Globals::zp_flags
+    bpl @end
+
+    ;; Save registers.
+    pha
+    txa
+    pha
+    tya
+    pha
+
+    lda #$00
+    sta OAM::ADDRESS
+    lda #$02
+    sta OAM::DMA
+
+    bit PPU::STATUS
+    lda #$00
+    sta PPU::SCROLL
+    sta PPU::SCROLL
+
+    lda #%01111111
+    and Globals::zp_flags
+    sta Globals::zp_flags
+
+    ;; Restore registers.
+    pla
+    tay
+    pla
+    tax
+    pla
+
+@end:
+    rti
+.endproc
+
+;; Unused.
+.proc irq
+    rti
+.endproc
-- 
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