From 1d1f08646352df00977a88adb99e04d54e4dfd5d Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <msabate@suse.com>
Date: Tue, 2 Apr 2024 22:02:59 +0200
Subject: basics: Add a flickering example
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Add an example on how to flicker sprites so to not surpass the scanline
limit for them.

Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>
---
 shared/diskun.s | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 shared/diskun.s

(limited to 'shared/diskun.s')

diff --git a/shared/diskun.s b/shared/diskun.s
new file mode 100644
index 0000000..d8bab90
--- /dev/null
+++ b/shared/diskun.s
@@ -0,0 +1,95 @@
+;;; Simple sprite that can be moved with the dpad easily. Use it to have
+;;; something funny moving.
+
+.include "joypad.s"
+
+.scope Diskun
+    m_screen_x = $30
+    m_screen_y = $31
+
+    .proc init_palettes
+        lda #$3F
+        sta $2006                   ; PPUADDR
+        lda #$00
+        sta $2006                   ; PPUADDR
+
+        ldx #0
+    @load_palettes_loop:
+        lda palettes, x
+        sta $2007                   ; PPUDATA
+        inx
+        cpx #$20
+        bne @load_palettes_loop
+        rts
+    palettes:
+        DEFAULT_COLOR = $11
+
+        ;; Background
+        .byte DEFAULT_COLOR, $36, $17, $0F
+        .byte DEFAULT_COLOR, $00, $00, $00
+        .byte DEFAULT_COLOR, $00, $00, $00
+        .byte DEFAULT_COLOR, $00, $00, $00
+
+        ;; Foreground
+        .byte DEFAULT_COLOR, $28, $0F, $30
+        .byte DEFAULT_COLOR, $00, $00, $00
+        .byte DEFAULT_COLOR, $00, $00, $00
+        .byte DEFAULT_COLOR, $00, $00, $00
+
+        rts
+    .endproc
+
+    .proc update
+        lda #Joypad::BUTTON_UP
+        and Joypad::m_buttons1
+        beq @check_down
+
+        dec Diskun::m_screen_y
+        dec Diskun::m_screen_y
+        jmp @check_left
+    @check_down:
+        lda #Joypad::BUTTON_DOWN
+        and Joypad::m_buttons1
+        beq @check_left
+
+        inc Diskun::m_screen_y
+        inc Diskun::m_screen_y
+    @check_left:
+        lda #Joypad::BUTTON_LEFT
+        and Joypad::m_buttons1
+        beq @check_right
+
+        dec Diskun::m_screen_x
+        dec Diskun::m_screen_x
+    @check_right:
+        lda #Joypad::BUTTON_RIGHT
+        and Joypad::m_buttons1
+        beq @end
+
+        inc Diskun::m_screen_x
+        inc Diskun::m_screen_x
+    @end:
+        rts
+    .endproc
+
+    .proc nmi_update
+        lda Diskun::m_screen_x
+        sta $203
+        sta $20B
+        clc
+        adc #8
+        sta $207
+        sta $20F
+
+        lda Diskun::m_screen_y
+        sta $200
+        sta $204
+        clc
+        adc #8
+        sta $208
+        sta $20C
+
+        rts
+    .endproc
+.endscope
+
-- 
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