From ec5c6b2becdc2232ec83a2c7c5a672cc534c1001 Mon Sep 17 00:00:00 2001
From: shylie <shylie@shylie.info>
Date: Sat, 18 Apr 2026 12:21:04 -0400
Subject: [PATCH] Fix bug in update

---
 src/main.cpp | 48 ++++++++++++++++++++++++++++++++++--------------
 src/sand.cpp |  2 +-
 2 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 512a981..f6ed8a4 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -7,29 +7,46 @@
 #include <SDL3/SDL_video.h>
 #include <sand.h>
 
-constexpr uint16_t WIDTH = 128;
-constexpr uint16_t HEIGHT = 128;
+constexpr uint16_t WIDTH = 256;
+constexpr uint16_t HEIGHT = 256;
 
 constexpr int WINDOW_WIDTH = 1024;
 constexpr int WINDOW_HEIGHT = 1024;
 
 uint8_t lookup[][3]
-  = { { 0, 0, 0 }, { 50, 0, 0 }, { 100, 100, 100 }, { 200, 200, 200 } };
+  = { { 0, 0, 0 }, { 50, 0, 0 }, { 100, 100, 100 }, { 100, 100, 100 } };
 
 int main(int argc, char** argv)
 {
   auto rb = sand::TypeBuilder()
               .add_type("offgrid")
               .add_type("air")
-              .add_type("stone1")
-              .add_type("stone2")
+              .add_type("stone1", "stone2")
+              .add_type("stone2", "stone1")
               .finish();
 
-  rb.add_rule("air", "stone1")
+  rb.add_rule("air", "stone2")
     .top_middle([](const auto& t) { return t == "stone1"; });
+  rb.add_rule("air", "stone1")
+    .top_middle([](const auto& t) { return t == "stone2"; });
+  rb.add_rule("air", "stone2")
+    .top_right([](const auto& t) { return t == "stone1"; })
+    .middle_right([](const auto& t) { return t != "air"; });
+  rb.add_rule("air", "stone1")
+    .top_left([](const auto& t) { return t == "stone2"; })
+    .middle_left([](const auto& t) { return t != "air"; });
 
   rb.add_rule("stone1", "air")
     .bottom_middle([](const auto& t) { return t == "air"; });
+  rb.add_rule("stone1", "air")
+    .bottom_left([](const auto& t) { return t == "air"; })
+    .bottom_middle([](const auto& t) { return t != "air"; });
+
+  rb.add_rule("stone2", "air")
+    .bottom_middle([](const auto& t) { return t == "air"; });
+  rb.add_rule("stone2", "air")
+    .bottom_right([](const auto& t) { return t == "air"; })
+    .bottom_middle([](const auto& t) { return t != "air"; });
 
   auto s = rb.build(WIDTH, HEIGHT, "air");
 
@@ -60,15 +77,20 @@ int main(int argc, char** argv)
 
     float x, y;
     int state;
-    if (time > 0.008 && (state = SDL_GetMouseState(&x, &y)))
+    if (time > 1 / 1000.0f)
     {
-      int ix = x * WIDTH / WINDOW_WIDTH;
-      int iy = y * HEIGHT / WINDOW_HEIGHT;
+      time = 0;
+      s.update();
 
-      if (ix >= 0 && ix < WIDTH && iy >= 0 && iy < HEIGHT)
+      if ((state = SDL_GetMouseState(&x, &y)))
       {
-        time = 0;
-        s.set(ix, iy, state == 1 ? "stone1" : "stone2");
+        int ix = x * WIDTH / WINDOW_WIDTH;
+        int iy = y * HEIGHT / WINDOW_HEIGHT;
+
+        if (ix >= 0 && ix < WIDTH && iy >= 0 && iy < HEIGHT)
+        {
+          s.set(ix, iy, state == 1 ? "stone1" : "stone2");
+        }
       }
     }
 
@@ -85,8 +107,6 @@ int main(int argc, char** argv)
     SDL_BlitSurfaceScaled(surface, nullptr, SDL_GetWindowSurface(window),
                           nullptr, SDL_SCALEMODE_NEAREST);
     SDL_UpdateWindowSurface(window);
-
-    s.update();
   }
 
   SDL_DestroySurface(surface);
diff --git a/src/sand.cpp b/src/sand.cpp
index 7a382eb..1da5270 100644
--- a/src/sand.cpp
+++ b/src/sand.cpp
@@ -291,7 +291,7 @@ void Sand::update()
 
     if (i < width - 1 && j > 0)
     {
-      neighbors += get(i + 1, j);
+      neighbors += get(i + 1, j - 1);
     }
     neighbors <<= 16;