From fc6a230af73d3689062ede031cbeef20b6e5d7f0 Mon Sep 17 00:00:00 2001
From: Luxferre <lux@ferre>
Date: Mon, 12 Jan 2026 10:55:03 +0200
Subject: [PATCH] entropy management for NES port

---
 nes/eznes.h       | 25 +++++++++++++++++--------
 nes/nescoundrel.c |  2 +-
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/nes/eznes.h b/nes/eznes.h
index d79301a..5a0db45 100644
--- a/nes/eznes.h
+++ b/nes/eznes.h
@@ -40,6 +40,13 @@
 #define NES_GREEN  0x28
 #define NES_YELLOW 0x2A
 
+/* RNG stuff */
+static u16 _ez_entropy = 0;
+
+u16 ezrand() {
+  return ((u16) rand()) ^ _ez_entropy;
+}
+
 /* Graphics section */
 
 void ppu_off() {
@@ -58,6 +65,7 @@ u8 joy_input_wait() {
   while(joy_read(JOY_1));
   /* wait for a new press */
   while(1) {
+    ++_ez_entropy;
     joy = joy_read(JOY_1);
     pressed = joy & ~last_joy;
     if(pressed & JOY_UP_MASK) return EZJOY_UP;
@@ -141,9 +149,6 @@ void init_sound() {
 /* Game initialization section */
 
 void init_game(u8 bg, u8 c1, u8 c2, u8 c3, u8 c4) {
-#ifdef _randomize
-  _randomize();
-#endif
   init_sound();
   bgcolor(COLOR_BLACK);
   textcolor(0);
@@ -156,6 +161,7 @@ void init_game(u8 bg, u8 c1, u8 c2, u8 c3, u8 c4) {
 void wait_for_start() {
   u8 joy;
   while(1) {
+    ++_ez_entropy;
     joy = joy_read(JOY_1);
     if(JOY_START(joy)) break;
     waitvsync();
@@ -165,14 +171,17 @@ void wait_for_start() {
 /* randomize until Start is pressed */
 void wait_for_start_rand() {
   u8 joy;
-  u16 entropy = rand();
+#ifdef _randomize
+  _randomize();
+#endif
+  _ez_entropy = rand();
   while(1) {
-    ++entropy;
+    ++_ez_entropy;
     joy = joy_read(JOY_1);
     if(JOY_START(joy)) break;
     waitvsync();
   }
-  srand(entropy);
+  srand(_ez_entropy);
 }
 
 /* Generic helper methods */
@@ -181,8 +190,8 @@ void wait_for_start_rand() {
 void shuffle(s8 *array, u16 n) {
   u16 i, j, t;
   if(n > 1) {
-    for(i=n-1;i>0;i--) {
-      j = (u16) (rand()%(i+1));
+    for(i=n-1;i>0;--i) {
+      j = (u16) (ezrand()%(i+1));
       t = array[j];
       array[j] = array[i];
       array[i] = t;
diff --git a/nes/nescoundrel.c b/nes/nescoundrel.c
index 923a2c5..1bdb99a 100644
--- a/nes/nescoundrel.c
+++ b/nes/nescoundrel.c
@@ -102,7 +102,7 @@ void win_screen(s16 score) {
   ppu_off();
   for(j=0;j<12;j+=4)
     for(i=3;i<32;i+=4)
-      colorxy(i, j, 1 + (rand() % 3));
+      colorxy(i, j, 1 + (ezrand() % 3));
   cputsxy(0, 3, "      ___ ___ ___ ______  \r\n" \
 "     |   Y   |   |   _  \\ \r\n" \
 "     |.  |   |.  |.  |   |\r\n" \