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

5 files changed, 230 insertions, 103 deletions

diff --git a/game/assets/pbullet.png b/game/assets/pbullet.png
new file mode 100644
index 0000000..e1ab048
--- /dev/null
+++ b/game/assets/pbullet.png
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
diff --git a/game/entities.asm b/game/entities.asm
index b3e1eea..eb9c44f 100644
--- a/game/entities.asm
+++ b/game/entities.asm
@@ -5,15 +5,35 @@
 .equ ET_NONE    0
 .equ ET_PLAYER  1
 .equ ET_ENEMY   2
+.equ ET_BULLET  3
 .equ ET_END     0xff
 
 .equ ET_BG      0xa000
 
-entities_erase:
-    ; bg is stored in ET_BG addr
-    ld b, >ET_BG
-    push b
+entities_init:
+    ld x, <entities
+    ld a, >entities
+
+    ; skip player
+    add x, 8
+    bo
+    inc a
+
+entities_init_next:
+    ld y, [a : x]
+    cmp y, ET_END
+    bz
+    ret
+
+    ld y, ET_NONE
+    ld [a : x], y
+
+    add x, 8
+    bo
+    inc a
+    jmp entities_init_next
 
+entities_erase:
     ld x, <entities
     ld a, >entities
 
@@ -21,8 +41,17 @@ entities_erase_next:
     ld y, [a : x]
     cmp y, ET_END
     bz
-    jmp entities_erase_done
+    ret
+    cmp y, 0
+    bnz
+    jmp entities_erase_in_use
+
+    add x, 8
+    bo
+    inc a
+    jmp entities_erase_next
 
+entities_erase_in_use:
     ; settings mode
     ld y, 128
     ld b, 0xb0
@@ -32,9 +61,9 @@ entities_erase_next:
     inc b
 
     ; addr: bg data
-    ld y, 0
+    ld y, <ET_BG
     port b, y
-    ld y, [sp + 0]
+    ld y, >ET_BG
     port b, y
 
     ; x
@@ -66,17 +95,8 @@ entities_erase_next:
     add x, 6
     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
@@ -86,7 +106,16 @@ entities_update_next:
     cmp y, ET_END
     bz
     ret
+    cmp y, 0
+    bnz
+    jmp entities_update_in_use
+
+    add x, 8
+    bo
+    inc a
+    jmp entities_update_next
 
+entities_update_in_use:
     push a
     push x
 
@@ -124,10 +153,6 @@ entities_update_next:
     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
 
@@ -135,30 +160,19 @@ entities_draw_next:
     ld y, [a : x]
     cmp y, ET_END
     bz
-    jmp entities_draw_done
-
-    ; two local variables to keep x, y coord
-
-    inc x
-    bo
-    inc a
-    ld y, [a : x]
-    ; x coord
-    push y
+    ret
+    cmp y, 0
+    bnz
+    jmp entities_draw_in_use
 
-    inc x
+    add x, 8
     bo
     inc a
-    ld y, [a : x]
-    ; y coord
-    push y
+    jmp entities_draw_next
 
-    inc x
-    bo
-    inc a
-    ; a : x points to the frame
+entities_draw_in_use:
 
-    ; save bg data
+    ; draw sprite
 
     ; settings mode
     ld y, 128
@@ -168,49 +182,19 @@ entities_draw_next:
     ; setup
     inc b
 
-    ; addr: bg data saving space
-    ld y, 0
-    port b, y
-    ld y, [sp + 2]
-    port b, y
-
-    ; x
-    ld y, [sp + 1]
-    port b, y
-
-    ; y
-    ld y, [sp + 0]
-    port b, y
-
-    ; 16x16
-    ld y, 16
-    port b, y
-    port b, y
-
-    ; blit
-    dec b
-    ; read, no transparent
-    ld y, 4
-    port b, y
-
-    ; draw sprite
-
-    ; settings mode
-    ld y, 128
-    ld b, 0xb0
-    port b, y
+    push a
+    push x
 
-    ; setup
-    inc b
+    add x, 3
+    bo
+    inc a
 
-    ; prepare some local variables
+    ; frame number
+    ld b, [a : x]
 
-    ; frame
-    ld y, [a : x]
     inc x
     bo
     inc a
-    push y
 
     ; sprite addr
     ld y, [a : x]
@@ -219,19 +203,14 @@ entities_draw_next:
     bo
     inc a
     ld y, [a : x]
-    push y
 
-    ; frame number
-    ld b, [sp + 2]
 entity_draw_frame:
     dec b
     bo
     jmp entity_draw_frame_done
 
     ; calculate frame
-    ld y, [sp + 0]
     inc y
-    ld [sp + 0], y
     jmp entity_draw_frame
 
 entity_draw_frame_done:
@@ -239,23 +218,28 @@ entity_draw_frame_done:
     ; settings port
     ld b, 0xb1
 
+    ld x, y
+    pop y
+
     ; addr: sprite data
-    ld y, [sp + 1]
-    port b, y
-    ld y, [sp + 0]
     port b, y
+    port b, x
 
-    ; free local variables
-    pop y
-    pop y
-    pop y
+    pop x
+    pop a
+
+    inc x
+    bo
+    inc a
 
     ; x
-    ld y, [sp + 1]
+    ld y, [a : x]
     port b, y
-
+    inc x
+    bo
+    inc a
     ; y
-    ld y, [sp + 0]
+    ld y, [a : x]
     port b, y
 
     ; 16x16
@@ -269,20 +253,31 @@ entity_draw_frame_done:
     ld y, 3
     port b, y
 
-    pop y
-    pop y
-
     ; next entity
-    add x, 3
+    add x, 6
     bo
     inc a
+    jmp entities_draw_next
 
-    pop b
-    inc b
-    push b
+entities_new:
+    ld x, <entities
+    ld a, >entities
 
-    jmp entities_draw_next
+entities_new_loop:
+    ld y, [a : x]
+    cmp y, ET_END
+    ccf
+    bz
+    ret
+    cmp y, 0
+    bz
+    jmp entities_new_found
 
-entities_draw_done:
-    pop a
+    add x, 8
+    bo
+    inc a
+    jmp entities_new_loop
+
+entities_new_found:
+    scf 
     ret
diff --git a/game/main.asm b/game/main.asm
index 8373f37..365e381 100644
--- a/game/main.asm
+++ b/game/main.asm
@@ -61,7 +61,7 @@ game_loop:
 ; Setup the game after the menu
 ;
 init_game:
-    halt
+    call entities_init
 
     ; set player initial coordinates
     ld x, <player_coord
@@ -75,6 +75,8 @@ init_game:
     ld y, 104
     ld [a : x], y
 
+    halt
+
     call clear_screen
     call entities_draw
 
@@ -252,6 +254,7 @@ int_handler:
 .include "starfield.asm"
 .include "entities.asm"
 .include "player.asm"
+.include "bullet.asm"
 
 ;
 ; entity data
@@ -268,7 +271,7 @@ player_coord:
     .dw player_update
 
     ; 16 entities
-    .ds 112, 0
+    .ds 128, 0
 
     ; end of list
     .db ET_END
@@ -276,6 +279,8 @@ player_coord:
 ; sprite data
 player_sprite:
     .incpng "assets/player.png"
+pbullet_sprite:
+    .incpng "assets/pbullet.png"
 
 ; starfield data
 stars:
diff --git a/game/player.asm b/game/player.asm
index 0e44411..ef63839 100644
--- a/game/player.asm
+++ b/game/player.asm
@@ -2,6 +2,9 @@
 ; player update code
 ;
 
+cool_down:
+    .db 0
+
 player_update:
     ld x, [sp + 2]
     ld a, [sp + 3]
@@ -52,6 +55,8 @@ player_update:
     ; base frame
     ld y, 0
 
+    push b
+
     ; both left and right
     and b, 48
     cmp b, 48
@@ -69,4 +74,27 @@ player_update:
 
 player_store_frame:
     ld [a : x], y
+
+    pop b
+
+    ; fire
+    bit b, 0
+    bnz
+    ret
+
+    ld x, <cool_down
+    ld a, >cool_down
+    ld y, [a : x]
+    cmp y, 0
+    bz
+    jmp player_fire
+    dec y
+    ld [a : x], y
+    ret
+
+player_fire:
+    add y, 10
+    ld [a : x], y
+
+    call bullet_player_new
     ret