diff --git a/src/app/asm/script.cc b/src/app/asm/script.cc
index c55b1935..6203353f 100644
--- a/src/app/asm/script.cc
+++ b/src/app/asm/script.cc
@@ -10,6 +10,7 @@
 
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
+#include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "app/core/constants.h"
 #include "app/rom.h"
@@ -18,30 +19,97 @@ namespace yaze {
 namespace app {
 namespace snes_asm {
 
-absl::Status Script::ApplyPatchToROM(ROM& rom) {
-  char* data = (char*) rom.data();
-  int size = 0;
+static auto string_replace(std::string &str, const std::string &from,
+                           const std::string &to) -> bool {
+  size_t start = str.find(from);
+  if (start == std::string::npos) return false;
+
+  str.replace(start, from.length(), to);
+  return true;
+}
+
+std::string GenerateBytePool(char mosaic_tiles[core::kNumOverworldMaps]) {
+  std::string to_return = "";
+  int column = 0;
+  for (int i = 0; i < core::kNumOverworldMaps; ++i) {
+    std::string to_add = "";
+
+    // if start of line, define byte
+    if (i == 0 || i % 8 == 0) {
+      to_add += "  db ";
+    }
+
+    // set byte
+    to_add += "$00";
+    if (mosaic_tiles[i] > 0) {
+      if (i == 0 || i % 8 == 0) {
+        to_add = "  db $01";
+      } else {
+        to_add = "$01";
+      }
+    }
+
+    // newline or comma separated
+    if (column == 7) {
+      column = 0;
+      to_add += " \n";
+    } else {
+      column++;
+      to_add += ", ";
+    }
+
+    to_return += to_add;
+  }
+  return to_return;
+}
+
+absl::Status Script::ApplyPatchToROM(ROM &rom) {
+  char *data = (char *)rom.data();
+  int size = rom.GetSize();
+  int count = 0;
   if (!asar_patch(patch_filename_.c_str(), data, patch_size_, &size)) {
-    return absl::InternalError("Unable to apply patch");
+    auto asar_error = asar_geterrors(&count);
+    auto full_error = asar_error->fullerrdata;
+    return absl::InternalError(absl::StrCat("ASAR Error: ", full_error));
   }
   return absl::OkStatus();
 }
 
-absl::StatusOr<absl::string_view> Script::GenerateMosaicChangeAssembly(
-    std::array<int, core::kNumOverworldMaps> mosaic_tiles) {
+absl::Status Script::GenerateMosaicChangeAssembly(
+    ROM &rom, char mosaic_tiles[core::kNumOverworldMaps], int routine_offset) {
   std::fstream file("assets/asm/mosaic_change.asm",
                     std::ios::out | std::ios::in);
   if (!file.is_open()) {
     return absl::InvalidArgumentError(
         "Couldn't open mosaic change template file");
   }
-  std::stringstream assembly;
-  assembly << "org ";
-  assembly << kDefaultMosaicHook;
-  assembly << file.rdbuf();
 
+  std::stringstream assembly;
+  assembly << file.rdbuf();
   file.close();
-  return assembly.str();
+
+  auto assembly_string = assembly.str();
+  if (!string_replace(assembly_string, "<HOOK>", kMosaicChangeOffset)) {
+    return absl::InternalError(
+        "Mosaic template did not have proper `<HOOK>` to replace.");
+  }
+
+  if (!string_replace(
+          assembly_string, "<EXPANDED_SPACE>",
+          absl::StrFormat("$%x", routine_offset + kSNESToPCOffset))) {
+    return absl::InternalError(
+        "Mosaic template did not have proper `<EXPANDED_SPACE>` to replace.");
+  }
+
+  assembly_string += GenerateBytePool(mosaic_tiles);
+  patch_filename_ = "assets/asm/mosaic_change_generated.asm";
+  std::ofstream new_file(patch_filename_, std::ios::out);
+  if (new_file.is_open()) {
+    new_file.write(assembly_string.c_str(), assembly_string.size());
+    new_file.close();
+  }
+
+  return ApplyPatchToROM(rom);
 }
 
 }  // namespace snes_asm
diff --git a/src/app/asm/script.h b/src/app/asm/script.h
index af6a9836..e5edcfe9 100644
--- a/src/app/asm/script.h
+++ b/src/app/asm/script.h
@@ -11,6 +11,7 @@
 
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
+#include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "app/core/constants.h"
 #include "app/rom.h"
@@ -19,18 +20,19 @@ namespace yaze {
 namespace app {
 namespace snes_asm {
 
-constexpr char kDefaultMosaicHook[] = "$02AADB";
+const std::string kMosaicChangeOffset = "$02AADB";
+constexpr int kSNESToPCOffset = 0x138000;
 
 class Script {
  public:
-  Script() { asar_init_with_dll_path("C:/Users/starw/Code/yaze/assets/asar.dll"); }
+  Script() { asar_init_with_dll_path("assets/libasar.dll"); }
 
-  absl::Status ApplyPatchToROM(ROM& rom);
-
-  absl::StatusOr<absl::string_view> GenerateMosaicChangeAssembly(
-      std::array<int, core::kNumOverworldMaps> mosaic_tiles);
+  absl::Status GenerateMosaicChangeAssembly(
+      ROM& rom, char mosaic_tiles[core::kNumOverworldMaps], int routine_offset);
 
  private:
+  absl::Status ApplyPatchToROM(ROM& rom);
+
   int64_t patch_size_;
   std::string patch_filename_;
   std::string patch_contents_;