From d975c16ed7ad39a3caf32452c54cee57f7ffb5b2 Mon Sep 17 00:00:00 2001
From: Stevan Freeborn <stevan.freeborn@gmail.com>
Date: Sat, 18 Jul 2026 15:15:55 -0500
Subject: [PATCH] fix(cpu): add key register and font address bounds checks

---
 main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index 6b66b59..059ce78 100644
--- a/main.c
+++ b/main.c
@@ -389,11 +389,11 @@ int main(int argc, char *argv[]) {
           break;
         case 57344: // E000
           if (nn == 158) {
-            if (chip->keys[chip->V[x]] == 1) {
+            if (chip->keys[chip->V[x] & 0x0F] == 1) {
               chip->pc += 2;
             }
           } else if (nn == 161) {
-            if (chip->keys[chip->V[x]] != 1) {
+            if (chip->keys[chip->V[x] & 0x0F] != 1) {
               chip->pc += 2;
             }
           }
@@ -411,7 +411,7 @@ int main(int argc, char *argv[]) {
           } else if (nn == 30) {
             chip->I += chip->V[x];
           } else if (nn == 41) {
-            chip->I = FONT_START + (chip->V[x] * 5);
+            chip->I = FONT_START + ((chip->V[x] & 0x0F) * 5);
           } else if (nn == 51) {
             chip->memory[chip->I] = chip->V[x] / 100;
             chip->memory[chip->I + 1] = (chip->V[x] / 10) % 10;