Add player bullets

Also a changes in the entity system:

- don't preserve the BG (always erase black)
- skip unused entities
- fix in the reserved size (and entity is 8 bytes)
- allocate new entities

1 files changed, 99 insertions, 0 deletions

diff --git a/game/bullet.asm b/game/bullet.asm
new file mode 100644
index 0000000..c2b55cd
--- /dev/null
+++ b/game/bullet.asm
@@ -0,0 +1,99 @@
+;
+; Player bullets
+;
+bullet_player_new:
+    call entities_new
+    bnc
+    ret
+
+    ; a : x points to the entity
+
+    ld y, ET_BULLET
+    ld [a : x], y
+
+    inc x
+    bo
+    inc a
+
+    ; caller entity is in the stack
+    ld y, [sp + 4]
+    ld b, [sp + 5]
+
+    inc y
+    bo
+    inc b
+    push y
+    ld y, [b : y]
+    ; same x
+    ld [a : x], y
+    pop y
+
+    inc x
+    bo
+    inc a
+
+    inc y
+    bo
+    inc b
+    ld y, [b : y]
+    ; same y
+    ld [a : x], y
+
+    inc x
+    bo
+    inc a
+
+    ; frame 0
+    ld y, 0
+    ld [a : x], y 
+
+    inc x
+    bo
+    inc a
+
+    ; player bullet sprite
+    ld y, <pbullet_sprite
+    ld [a : x], y
+    inc x
+    bo
+    inc a
+    ld y, >pbullet_sprite
+    ld [a : x], y
+
+    inc x
+    bo
+    inc b
+
+    ; update function
+    ld y, <pbullet_update
+    ld [a : x], y
+    inc x
+    bo
+    inc a
+    ld y, >pbullet_update
+    ld [a : x], y
+
+    ret
+
+pbullet_update:
+    ld x, [sp + 2]
+    ld a, [sp + 3]
+
+    add x, 2
+    bo
+    inc a
+
+    ld y, [a : x]
+    sub y, 2
+    bo
+    jmp pbullet_done
+    ld [a : x], y
+    ret
+
+pbullet_done:
+    ld x, [sp + 2]
+    ld a, [sp + 3]
+
+    ld y, ET_NONE
+    ld [a : x], y
+    ret