From d532317c011b9e5653241d50b961ee8caa710144 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Tue, 9 May 2023 22:43:33 +0100
Subject: Playground

Potential example game.
---
 game/entities.asm | 263 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 263 insertions(+)
 create mode 100644 game/entities.asm

(limited to 'game/entities.asm')

diff --git a/game/entities.asm b/game/entities.asm
new file mode 100644
index 0000000..fa9d8fd
--- /dev/null
+++ b/game/entities.asm
@@ -0,0 +1,263 @@
+;
+; Simple array based entity system
+;
+
+.equ ET_NONE    0
+.equ ET_PLAYER  1
+.equ ET_ENEMY   2
+.equ ET_END     0xff
+
+.equ ET_BG      0xa000
+
+entities_erase:
+    ; bg is stored in ET_BG addr
+    ld b, >ET_BG
+    push b
+
+    ld x, <entities
+    ld a, >entities
+
+entities_erase_next:
+    ld y, [a : x]
+    cmp y, ET_END
+    bz
+    jmp entities_erase_done
+
+    ; write, no transparent
+    ld y, 1
+    push y
+
+    ; dst: x
+    inc x
+    bo
+    inc a
+    ld y, [a : x]
+    push y
+
+    ; dst: y
+    inc x
+    bo
+    inc a
+    ld y, [a : x]
+    push y
+
+    ; src: saved bg
+    ld y, [sp + 3]
+    push y
+    ld y, 0
+    push y
+
+    call entities_blt
+
+    pop y
+    pop y
+    pop y
+    pop y
+    pop y
+
+    ; next entity
+    add x, 5
+    bo
+    inc a
+
+    pop b
+    inc b
+    push b
+
+    jmp entities_erase_next
+
+entities_erase_done:
+    pop a
+    ret
+
+entities_update:
+    ld x, <entities
+    ld a, >entities
+
+entities_update_next:
+    ld y, [a : x]
+    cmp y, ET_END
+    bz
+    ret
+
+    push a
+    push x
+
+    add x, 5
+    bo
+    inc a
+
+    ld y, [a : x]
+    inc x
+    bo
+    inc a
+    ld b, [a : x]
+    inc x
+    bo
+    inc a
+
+    ld x, [sp + 0]
+    ld a, [sp + 1]
+
+    ; entity update
+    push a
+    push x
+    call [b : y]
+    pop x
+    pop x
+
+    pop x
+    pop a
+
+    add x, 7
+    bo
+    inc a
+
+    jmp entities_update_next
+
+entities_draw:
+    ; bg is stored in ET_BG addr
+    ld b, >ET_BG
+    push b
+
+    ld x, <entities
+    ld a, >entities
+
+entities_draw_next:
+    ld y, [a : x]
+    cmp y, ET_END
+    bz
+    jmp entities_draw_done
+
+    inc x
+    bo
+    inc a
+    ; save x addr for later
+    push a
+    push x
+
+    ; save bg
+
+    ; read, no transparent
+    ld y, 4
+    push y
+
+    ; dst: x
+    ld y, [a : x]
+    push y
+
+    ; dst: y
+    inc x
+    bo
+    inc a
+    ld y, [a : x]
+    push y
+
+    ; dst: save bg
+    ld y, [sp + 5]
+    push y
+    ld y, 0
+    push y
+
+    call entities_blt
+
+    pop y
+    pop y
+    pop y
+    pop y
+    pop y
+
+    ; draw sprite
+
+    ; x addr
+    pop x
+    pop a
+
+    ; write, transparent
+    ld y, 3
+    push y
+
+    ; dst: x
+    ld y, [a : x]
+    push y
+
+    ; dst: y
+    inc x
+    bo
+    inc a
+    ld y, [a : x]
+    push y
+
+    ; src: the sprite
+    inc x
+    bo
+    inc a
+    ld y, [a : x]
+    inc x
+    bo
+    inc a
+    ld b, [a : x]
+    push b
+    push y
+
+    call entities_blt
+
+    pop y
+    pop y
+    pop y
+    pop y
+    pop y
+
+    ; next entity
+    add x, 3
+    bo
+    inc a
+
+    pop b
+    inc b
+    push b
+
+    jmp entities_draw_next
+
+entities_draw_done:
+    pop a
+    ret
+
+; sp: write mode
+;     y coord
+;     x coord
+;     addr
+entities_blt:
+    ; settings mode
+    ld y, 128
+    ld b, 0xb0
+    port b, y
+
+    ; setup
+    inc b
+
+    ; addr
+    ld y, [sp + 2]
+    port b, y
+    ld y, [sp + 3]
+    port b, y
+
+    ; x
+    ld y, [sp + 5]
+    port b, y
+    ; y
+    ld y, [sp + 4]
+    port b, y
+
+    ; 16x16
+    ld y, 16
+    port b, y
+    port b, y
+
+    ; blit
+    dec b
+    ; write mode
+    ld y, [sp + 6]
+    port b, y
+    ret
+
-- 
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