From 2bb1bc161d3cec45f5fd2ff71128d257dfbd3a6e Mon Sep 17 00:00:00 2001
From: Colin McMillen <c@16bit.cc>
Date: Mon, 1 Jun 2015 00:18:03 -0400
Subject: [PATCH] Add multiple enemy shots.

---
 memory.asm |  4 ++--
 pewpew.asm | 27 ++++++++++++++++++++-------
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/memory.asm b/memory.asm
index a268167..ae3c391 100644
--- a/memory.asm
+++ b/memory.asm
@@ -13,7 +13,7 @@
 ; 0030-003F: (x, y) velocities of each of the 8 possible shot states.
 ; 0040-009F: {sprite, x, y, x-velocity, y-velocity, unused} per player shot.
 ;            If sprite is 0, the shot is disabled.
-; 00A0-00FF: As above, for enemy shots.
+; 00A0-015F: As above, for enemy shots.
 ; [gap]
 ; Sprite table buffers -- copied each frame to OAM during VBlank, using DMA.
 ; 1000-11FF: table 1 (4 bytes each: x/y coord, tile #, flip/priority/palette)
@@ -34,7 +34,7 @@
 .define playerShotArray $40
 .define playerShotArrayLength 16
 .define enemyShotArray $A0
-.define enemyShotArrayLength 16
+.define enemyShotArrayLength 32
 .define shotSize 6
 
 .define numSprites 128
diff --git a/pewpew.asm b/pewpew.asm
index 5604b64..ddbb02d 100644
--- a/pewpew.asm
+++ b/pewpew.asm
@@ -488,22 +488,35 @@ UpdateShotCooldown:
 
 SpawnEnemyShots:
     lda vBlankCounter
-    bit #%00111111
+    bit #%00001111
     beq +
     rts
++
+    ldy #0
+-
+    lda enemyShotArray, Y
+    cmp #0
+    beq +
+    .rept 6
+        iny
+    .endr
+    cpy #(enemyShotArrayLength * shotSize)
+    bne -
+    rts  ; Too many shots; bail.
+
 +
     lda #12  ; Sprite number.
-    sta enemyShotArray
+    sta enemyShotArray, Y
 
     lda #254
-    sta enemyShotArray + 1  ; x.
+    sta enemyShotArray + 1, Y  ; x.
 
     lda #((224 - 32) / 2)
     and #%01111111
-    sta enemyShotArray + 2  ; y.
+    sta enemyShotArray + 2, Y  ; y.
 
-    lda #-6
-    sta enemyShotArray + 3  ; x-velocity.
+    lda #-4
+    sta enemyShotArray + 3, Y  ; x-velocity.
 
     GetRandomByte
     and #%00000111  ; [0, 7]
@@ -513,7 +526,7 @@ SpawnEnemyShots:
     bne +
     lda #0  ; [-3, 3] with 2x chance of zero.
 +
-    sta enemyShotArray + 4  ; y-velocity.
+    sta enemyShotArray + 4, Y  ; y-velocity.
     rts