From 6a4219d3733c613b12e973244d84f2fe7181dbff Mon Sep 17 00:00:00 2001
From: Kieran Klukas <me@dunkirk.sh>
Date: Wed, 25 Mar 2026 16:14:48 -0400
Subject: [PATCH] bug: vector overflow on width

---
 physics_engine.vhd |  9 +++++----
 visualizer.py      | 10 +++++-----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/physics_engine.vhd b/physics_engine.vhd
index a1d75b6..a96e367 100644
--- a/physics_engine.vhd
+++ b/physics_engine.vhd
@@ -192,8 +192,9 @@ begin
         end if;
 
         -- == LEFT WALL ==
-        if px(9) = '1' or px <= LEFT_WALL then
-            px := LEFT_WALL;
+        -- Detect underflow: moving left (vx negative) but px wrapped to > pos_x
+        if (vx(9) = '1' and px > pos_x) or px <= LEFT_WALL + SIZE then
+            px := LEFT_WALL + SIZE;
             bounced := '1'; bounce_wall := '1';
             bounce_speed := (not vx) + 1;
             vx := (not vx) + 1;
@@ -203,8 +204,8 @@ begin
         end if;
 
         -- == RIGHT WALL ==
-        if px >= RIGHT_WALL then
-            px := RIGHT_WALL;
+        if px >= RIGHT_WALL - SIZE then
+            px := RIGHT_WALL - SIZE;
             bounced := '1'; bounce_wall := '1';
             bounce_speed := vx;
             vx := (not vx) + 1;
diff --git a/visualizer.py b/visualizer.py
index 25a4b4f..e8d31e5 100644
--- a/visualizer.py
+++ b/visualizer.py
@@ -32,7 +32,7 @@ BOUNCE_SHIFT = 3  # energy loss = vel >> 3 (keep 87.5%)
 GROUND = 440
 CEILING = 16
 LEFT_WALL = 8
-RIGHT_WALL = 620
+RIGHT_WALL = 631
 GROUND_TOP = 448
 CEIL_BOT = 8
 
@@ -215,8 +215,8 @@ def main():
             vy = to_unsigned(svy)
 
         # --- Left wall bounce ---
-        if px <= LEFT_WALL:
-            px = LEFT_WALL
+        if px <= LEFT_WALL + SIZE:
+            px = LEFT_WALL + SIZE
             bounced = True; bounce_wall = True
             bounce_speed = abs(to_signed(vx))
             vx = negate(vx)
@@ -226,8 +226,8 @@ def main():
             vx = to_unsigned(svx)
 
         # --- Right wall bounce ---
-        if px >= RIGHT_WALL:
-            px = RIGHT_WALL
+        if px >= RIGHT_WALL - SIZE:
+            px = RIGHT_WALL - SIZE
             bounced = True; bounce_wall = True
             bounce_speed = abs(to_signed(vx))
             vx = negate(vx)
-- 
2.51.2