From 2cef3f08d11c40dfe755a98b13f1702e5a503e9a Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Thu, 9 Oct 2014 13:29:49 -0400
Subject: let the snake eat the apple

---
 main.s | 59 +++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 41 insertions(+), 18 deletions(-)

diff --git a/main.s b/main.s
index 55948b4..f5b4e2c 100644
--- a/main.s
+++ b/main.s
@@ -291,23 +291,43 @@ apply_direction:
 check_collisions
   LDY #$00
   LDA (head), y
-  CMP #$40
+  TAX
+  LDY #$01
+  LDA (head), y
+  TAY
+
+  CPX #$40
   BCC collision
-  CMP #$C0
+  CPX #$C0
   BCS collision
 
-  LDY #$01
-  LDA (head), y
-  CMP #$3D
+  CPY #$3D
   BCC collision
-  CMP #$BD
+  CPY #$BD
   BCS collision
 
+  CPX apple.x
+  BEQ maybe_eat_apple
+
   JMP end_game_loop
 
 collision:
   JSR end_game
 
+  JMP end_game_loop
+
+maybe_eat_apple:
+  CPY apple.y
+  BEQ eat_apple
+
+  JMP end_game_loop
+
+eat_apple:
+  LDX length
+  INX
+  STX length
+  JSR new_apple
+
 end_game_loop:
   RTS ; }}}
 read_controller1: ; {{{
@@ -344,18 +364,7 @@ start_game: ; {{{
   LDY #$01
   STA (head), y
 
-  JSR rand
-  LDA rand_state
-  AND #%01111000
-  CLC
-  ADC #$40
-  STA apple.x
-  JSR rand
-  LDA rand_state
-  AND #%01111000
-  CLC
-  ADC #$3D
-  STA apple.y
+  JSR new_apple
 
 - BIT $2002
   BPL -
@@ -463,6 +472,20 @@ end_game: ; {{{
   LDA #$00
   STA game_state
   RTS ; }}}
+new_apple: ; {{{
+  JSR rand
+  LDA rand_state
+  AND #%01111000
+  CLC
+  ADC #$40
+  STA apple.x
+  JSR rand
+  LDA rand_state
+  AND #%01111000
+  CLC
+  ADC #$3D
+  STA apple.y
+  RTS ; }}}
 rand: ; {{{
   ; linear feedback shift register with taps at 8, 6, 5, and 4
   LDY rand_state
-- 
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