diff --git a/worthless/installer.py b/worthless/installer.py
index 7e9923d..3cf417a 100644
--- a/worthless/installer.py
+++ b/worthless/installer.py
@@ -28,10 +28,11 @@ async def _download_file(file_url: str, file_name: str, file_path: Path | str, f
     if overwrite:
         file_path.unlink(missing_ok=True)
     if file_path.exists():
-        cur_len = (file_path.stat()).st_size
-        headers |= {
+        with file_path.open("rb") as f:
+            cur_len = f.tell()
+        headers |= { 
             "Range": f"bytes={cur_len}-{file_len if file_len else ''}"
-        }
+        } 
     else:
         file_path.touch()
     print(f"Downloading {file_url} to {file_path}...")
@@ -458,10 +459,16 @@ class Installer:
         for _, segment in enumerate(game.latest.segments):
             archive_name = segment["path"].split("/")[-1]
             if self.temp_path.joinpath(archive_name + ".downloaded").exists() and self.temp_path.joinpath(archive_name).exists():
+                print(f"calculating md5 for downloaded game archive: {archive_name}")
+                md5 = calculate_md5(self.temp_path.joinpath(archive_name))
+                if md5 != segment["md5"]:
+                    print(f"mismatch md5 for downloaded game archive: {archive_name} ({md5}; expected {segment['md5']}), continuing anyway...")
                 continue
             await self._download_file(segment["path"], archive_name)
-            if calculate_md5(self.temp_path.joinpath(archive_name)) != segment["md5"]:
-                raise RuntimeError(f"mismatch md5 for downloaded game archive: {archive_name}")
+            print(f"calculating md5 for downloaded game archive: {archive_name}")
+            md5 = calculate_md5(self.temp_path.joinpath(archive_name))
+            if md5 != segment["md5"]:
+                print(f"mismatch md5 for downloaded game archive: {archive_name} ({md5}; expected {segment['md5']}), continuing anyway...")
             # if i != 0:
             #     with open(self.temp_path.joinpath(base_archive), 'ab') as f:
             #         with open(self.temp_path.joinpath(archive_name), 'rb') as f2:
@@ -512,7 +519,9 @@ class Installer:
 
         If `force_reinstall` is True, the game will be uninstalled then reinstalled.
         """
-        if self.get_game_data_path().exists():
+        if self.get_game_data_path().exists() \
+            and all([self._gamedir.joinpath(x).exists() for x in ["UnityPlayer.dll", "pkg_version"]]) \
+            and any([self._gamedir.joinpath(x).exists() for x in ["GenshinImpact.exe", "YuanShen.exe"]]):
             if not force_reinstall:
                 raise ValueError(f"Game is already installed in {self._gamedir}")
             await self.uninstall_game()