From 3746c4787b1ceaefe17deef143f38eab48bd5123 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Wed, 9 Oct 2024 12:46:47 +0200
Subject: [PATCH] Added simple game mode switch

---
 src/macros.inc | 13 +++++++++++++
 src/mem.s      |  5 +++++
 src/update.s   | 35 +++++++++++++++++++++++++++++++----
 src/wram.s     |  7 +++++++
 4 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/src/macros.inc b/src/macros.inc
index 9edc2d0..887ddbd 100644
--- a/src/macros.inc
+++ b/src/macros.inc
@@ -30,3 +30,16 @@
 
 ; relative jump: jr <label> RELB 
 #define REL - $ - 2 & 0xFF 
+
+#macro dblo 
+.db $1 & 0xFF
+#endmacro 
+
+#macro dbhi
+.db ($1 >> 8) & 0xFF 
+#endmacro 
+
+#macro dw 
+.db $1 & 0xFF
+.db ($1 >> 8) & 0xFF 
+#endmacro
diff --git a/src/mem.s b/src/mem.s
index 4a9dbdd..e536848 100644
--- a/src/mem.s
+++ b/src/mem.s
@@ -10,6 +10,11 @@ mem_init:
   ld hl, OAMDMAFN
   ld bc, shadow_oam_to_oam_end - shadow_oam_to_oam 
   call memcpy
+
+  ; set up game mode 
+  ld a, GM_GAME
+  ld [game_mode], a
+
   ret
 
 ; copies memory from one location to another 
diff --git a/src/update.s b/src/update.s
index aafc220..381a63b 100644
--- a/src/update.s
+++ b/src/update.s
@@ -1,11 +1,38 @@
+; update function table 
+update_table:
+dw update_game
+dw update_pause
+
+update_game:
+  ; update player
+  ld hl, player
+  call player_update
+
+  ret
+
+update_pause:
+  ret
+
   ; called after vblank
 update:
   ld a, [frame_count]
   inc a
   ld [frame_count], a
+  
+  ld a, [game_mode]
+  sla a ; * 2
+  ld d, 0
+  ld e, a
+  ld hl, update_table
+  add hl, de ; hl + index * 2
 
-  ; update player
-  ld hl, player
-  call player_update
+  ; hl = ptr to update routine 
+  ; => load functon ptr into hl
+  ld a, [hl+]
+  ld d, a
+  ld a, [hl]
+  ld l, d
+  ld h, a
+  ; hl = function value 
+  jp hl
 
-  ret
diff --git a/src/wram.s b/src/wram.s
index 8a9c8e1..392f56a 100644
--- a/src/wram.s
+++ b/src/wram.s
@@ -105,3 +105,10 @@ itmp: .adv 16
   ; timer for game over. when 
   ; it reaches 0 re-start game
 game_over_timer: .adv 1
+
+  ; game modes
+.se 0
+.de GM_GAME, 1
+.de GM_PAUSE, 1
+
+game_mode: .adv 1
-- 
2.30.2