From 14258fca4e18136cbc6e5d59e33c8f4e1ec884a2 Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Mon, 17 Mar 2025 02:32:14 -0700
Subject: [PATCH] Fix palette indexing bug

---
 src/f6502.c | 2 +-
 src/nes.c   | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/f6502.c b/src/f6502.c
index e054797..9f7377b 100644
--- a/src/f6502.c
+++ b/src/f6502.c
@@ -228,7 +228,7 @@ static inline int f6502_write(nes_Memory* mem,
                             pal[16] = pal[20] = pal[24] =
                             pal[28] = 0xFFU;
                     } else {
-                        pal[addr] = val;
+                        pal[addr] = val & 0x3FU;
                     }
 
                     // Memory-mapped mirroring
diff --git a/src/nes.c b/src/nes.c
index b7cd574..b2f6d17 100644
--- a/src/nes.c
+++ b/src/nes.c
@@ -87,8 +87,9 @@ static int nes_hsync(nes* sys, void* plat) {
         // Emulate the happy part of the backdrop override quirk
         int pal_idx = ((mem->addr & 0x3F00U) == 0x3F00U) ?
                       (mem->addr & 0x1FU) : 0;
+        LOGD("Background: %d", pal_idx);
         // Don't use the rendering palette (masked transparency)
-        status = nese_frame_start(plat, mem->pal_bank[0x300 + pal_idx]);
+        status = nese_frame_start(plat, mem->pal_bank[0x300 + pal_idx] & 0x3FU);
 
     }   break;