diff --git a/core_lib/game/argument.py b/core_lib/game/argument.py
new file mode 100644
index 0000000..3b6e8f9
--- /dev/null
+++ b/core_lib/game/argument.py
@@ -0,0 +1,151 @@
+import logging
+import shlex
+
+from core_lib.game.library import get_natives_platform_info
+
+logger = logging.getLogger("Launcher.CoreLib")
+
+def is_argument_allowed(argument: dict | str, allow_features: dict=dict) -> bool:
+    """
+    Check if argument is allowed or not.
+    :param argument:
+    :param allow_features: Should be like {key: value}
+    :return:
+        allowed: bool
+    """
+    if isinstance(argument, str):
+        return True
+
+    rules = argument.get('rules', {})
+
+    _, platform_rule_name, _ = get_natives_platform_info()
+
+    allowed = False
+
+    if not rules:
+        return True
+
+    for rule in rules:
+        rule_action = rule.get("action", None)
+        os_section = rule.get("os", {})
+        rule_os = os_section.get("name", None)
+        features_rule = rule.get("features", None)
+
+        if rule_os is not None and platform_rule_name != rule_os:
+            continue
+
+        matched = True
+
+        # Check feature dict
+        if features_rule:
+            for key, expected in features_rule.items():
+                if allow_features.get(key, False) != expected:
+                    matched = False
+                    break
+
+        if not matched:
+            continue
+
+
+        if rule_action == "allow":
+            allowed = True
+        elif rule_action == "disallow":
+            allowed = False
+        else:
+            logger.warning(f"Unknown action {rule_action}\n")
+
+    return allowed
+
+def replace_placeholders(argument, placeholders: dict) -> str:
+    if argument:
+        for key, value in placeholders.items():
+            argument = argument.replace("${" + key + "}", "" if value is None else str(value))
+
+    return argument
+
+class ArgumentMappings:
+    def __init__(self, player_name="Player", version_name="unknown",
+                 game_directory=None, assets_root=None, assets_index_name=None,
+                 auth_uuid="00000001-0002-0003-0004-000000000005",
+                 auth_access_token="", clientid=None, auth_xuid=None,
+                 user_type=None, version_type=None, natives_directory=None,
+                 launcher_name=None, launcher_version=None,
+                 classpath=None, classpath_separator=None, library_directory=None):
+        self.player_name = player_name
+        self.version_name = version_name
+        self.game_directory = game_directory
+        self.assets_root = assets_root
+        self.assets_index_name = assets_index_name
+        self.auth_uuid = auth_uuid
+        self.auth_access_token = auth_access_token
+        self.clientid = clientid
+        self.auth_xuid = auth_xuid
+        self.user_type = user_type
+        self.version_type = version_type
+        self.natives_directory = natives_directory
+        self.launcher_name = launcher_name
+        self.launcher_version = launcher_version
+        self.classpath = classpath
+        self.classpath_separator = classpath_separator
+        self.library_directory = library_directory
+
+    def generate_placeholders(self):
+        return {
+            "player_name": self.player_name,
+            "version_name": self.version_name,
+            "game_directory": self.game_directory,
+            "assets_root": self.assets_root,
+            "assets_index_name": self.assets_index_name,
+            "auth_uuid": self.auth_uuid,
+            "auth_access_token": self.auth_access_token,
+            "auth_player_name": self.player_name,
+            "clientid": self.clientid,
+            "auth_xuid": self.auth_xuid,
+            "user_type": self.user_type,
+            "version_type": self.version_type,
+            "natives_directory": self.natives_directory,
+            "launcher_name": self.launcher_name,
+            "launcher_version": self.launcher_version,
+            "classpath": self.classpath,
+            "classpath_separator": self.classpath_separator,
+            "library_directory": self.library_directory
+        }
+
+def convert_argument_to_multiple_string(argument: str | dict) -> list[str]:
+    if isinstance(argument, str):
+        return [argument]
+
+    if isinstance(argument, dict):
+        value = argument.get("value", None)
+
+        if isinstance(value, list):
+            return [str(item) for item in value] # ensure all item are string
+        elif isinstance(value, str):
+            return [value]
+
+    raise TypeError("Argument must be of type str or dict")
+
+def parse_and_generate_arguments(arguments: list | str, mappings: ArgumentMappings, features: dict=dict) -> list[str]:
+    parsed_arguments = []
+
+    if isinstance(arguments, str):
+        # Convert legacy argument into a list type
+        arguments = shlex.split(arguments)
+
+    placeholders = mappings.generate_placeholders()
+
+    for argument in arguments:
+        # Check rules
+        if not is_argument_allowed(argument, allow_features=features):
+            continue
+
+        # Each argument (section) may contain multiple items, convert it to list before replace placeholder
+        converted = convert_argument_to_multiple_string(argument)
+
+        for item in converted:
+            parsed = replace_placeholders(item, placeholders)
+            parsed_arguments.append(parsed)
+
+    return parsed_arguments
+
+
diff --git a/core_lib/game/asset.py b/core_lib/game/asset.py
index ec9bf17..acf7c11 100644
--- a/core_lib/game/asset.py
+++ b/core_lib/game/asset.py
@@ -13,6 +13,8 @@ from core_lib.game.version_info import find_useful_part_in_specific_version_mani
 
 MOJANG_RESOURCE_ENDPOINT = "https://resources.download.minecraft.net/{beginning}/{hash}"
 
+ASSET_DOWNLOAD_MAX_WORKERS = 20
+
 logger = logging.getLogger("Launcher.CoreLib")
 
 def fetch_asset_manifest(target_version_manifest: dict, raw=False) -> tuple[dict | bytes, str]:
@@ -84,7 +86,7 @@ def fetch_and_save_asset_manifest(target_version_manifest: dict, destination: Pa
         with file.path.open("wb") as f:
             f.write(data)
 
-        if sha1 is not None and not file.verify_sha1(sha1):
+        if sha1 and not file.verify_sha1(sha1):
             raise HashMismatchException(
                 "sha1",
                 file.sha1,
@@ -94,6 +96,7 @@ def fetch_and_save_asset_manifest(target_version_manifest: dict, destination: Pa
 
         return json.loads(data.decode("utf-8"))
     except Exception as e:
+        logger.exception(e)
         raise AssetManifestSaveException(
             "Error saving version manifest:\n{}".format(e)
         )
@@ -164,7 +167,14 @@ def download_assets_and_copy(assets: list[FileObject], legacy_assets: list[dict]
         files: list[FileObject] (files that download failed)
     """
 
-    fails , _ = download_multiple_files(assets, progress_callback=progress_callback)
+    fails , _ = download_multiple_files(assets, progress_callback=progress_callback,
+                                        max_workers=ASSET_DOWNLOAD_MAX_WORKERS)
+
+    if fails:
+        logger.warning(
+            "Download failed for assets: \n"
+            +"\n".join([asset.posix_path for asset in fails])
+        )
 
     for asset in legacy_assets:
         target = asset.get("target")
diff --git a/core_lib/game/version_info.py b/core_lib/game/version_info.py
index 7f77417..03da6bb 100644
--- a/core_lib/game/version_info.py
+++ b/core_lib/game/version_info.py
@@ -413,6 +413,7 @@ def fetch_and_save_version_manifest(dest: Path, target_version: str=None, root_m
 
         return data
     except Exception as e:
+        logger.exception(e)
         raise VersionManifestSaveException(
             "Error saving version manifest:\n{}".format(e)
         )
\ No newline at end of file
diff --git a/dialog/test.py b/dialog/test.py
index be9affc..43b1ccb 100644
--- a/dialog/test.py
+++ b/dialog/test.py
@@ -2,6 +2,7 @@ import json
 import textwrap
 import threading
 import time
+import traceback
 from pathlib import Path
 
 from PySide6.QtCore import Qt, QObject, Signal, Slot
@@ -11,7 +12,9 @@ from PySide6.QtWidgets import QPushButton, QVBoxLayout, QDialog, QPlainTextEdit,
 from core_lib.common.common import download_file, FileObject, download_multiple_files
 from core_lib.common.exception import VersionNotSelectedException, UnsupportedPlatformException, \
     NativeResolveException, DownloadException, DependencyException, VersionManifestFetchException, \
-    VersionManifestSaveException, NoSpecifiedVersionKeyException
+    VersionManifestSaveException, NoSpecifiedVersionKeyException, AssetManifestFetchException, \
+    AssetManifestSaveException, AssetDataKeyNotFoundException
+from core_lib.game.asset import fetch_and_save_asset_manifest, collect_assets_from_manifest, download_assets_and_copy
 from core_lib.game.library import collect_native_artifacts, download_libraries, unzip_natives, collect_library_artifacts
 
 from core_lib.game.version_info import (find_useful_part_in_specific_version_manifest,
@@ -48,6 +51,10 @@ class TestDialog(QDialog):
         self.button_4.setObjectName("ActionButton")
         self.button_4.clicked.connect(self.load_all_version)
 
+        self.button_5 = QPushButton("Download assets")
+        self.button_5.setObjectName("ActionButton")
+        self.button_5.clicked.connect(self.download_assets)
+
         self.ver_dropdown = QComboBox()
         self.ver_dropdown.setObjectName("Dropdown")
 
@@ -70,6 +77,7 @@ class TestDialog(QDialog):
         self.right_layout.addWidget(self.button)
         self.right_layout.addWidget(self.button_2)
         self.right_layout.addWidget(self.button_3)
+        self.right_layout.addWidget(self.button_5)
         self.right_layout.addStretch()
         self.right_layout.addWidget(self.ver_type_dropdown)
         self.right_layout.addWidget(self.ver_dropdown)
@@ -131,6 +139,10 @@ class TestDialog(QDialog):
             )
         )
 
+        self.widget_signal.show_and_print_error_message.connect(
+            self.show_and_print_error
+        )
+
         self.widget_signal.show_warning_message.connect(
             lambda msg: messagebox.warning(
                 self.parent,
@@ -185,6 +197,7 @@ class TestDialog(QDialog):
         update_vers_dropdown = Signal(list)
         update_types_dropdown = Signal(list)
         show_error_message = Signal(str)
+        show_and_print_error_message = Signal(dict)
         show_warning_message = Signal(str)
         show_info_message = Signal(str)
         enable_widget = Signal(object)
@@ -227,6 +240,25 @@ class TestDialog(QDialog):
         if isinstance(event, threading.Event):
             event.set()
 
+    @Slot(dict)
+    def show_and_print_error(self, context: dict):
+        error = context.get("error", None)
+        title = context.get("title", "Error")
+        message = context.get("message", "No content")
+
+        if isinstance(error, list):
+            self.app.logger.error("".join(error))
+        elif isinstance(error, str):
+            self.app.logger.error(error)
+        elif isinstance(error, Exception):
+            self.app.logger.exception(error)
+
+        messagebox.error(
+            self.parent,
+            title,
+            message=message
+        )
+
     @staticmethod
     def get_progress(value):
         width = 30
@@ -326,8 +358,12 @@ class TestDialog(QDialog):
                     """)
             self.output.setPlainText(content)
         except Exception as e:
-            self.widget_signal.show_error_message.emit(
-                "Failed to run test. Details: {}".format(e)
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Test Error",
+                    "message": "Failed to run test."
+                }
             )
         finally:
             self.button.setDisabled(False)
@@ -362,7 +398,25 @@ class TestDialog(QDialog):
             return
 
         thread = threading.Thread(
-            target=self._download_libraries_process,
+            target=self._download_libraries,
+            daemon=True,
+            args=(ver,)
+        )
+        thread.start()
+
+    def download_assets(self):
+        self.button_5.setDisabled(True)
+
+        self.output.clear()
+
+        ver = self.get_selected_version()
+
+        if not ver:
+            self.widget_signal.enable_widget.emit(self.button_5)
+            return
+
+        thread = threading.Thread(
+            target=self._download_assets,
             daemon=True,
             args=(ver,)
         )
@@ -444,8 +498,12 @@ class TestDialog(QDialog):
                 "Unable to save version manifest: {}".format(e.user_message),
             )
         except Exception as e:
-            self.widget_signal.show_error_message.emit(
-                "An unexpected error occurred while caching version manifest: {}".format(e),
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Cache Error",
+                    "message": "An unexpected error occurred while caching version manifest."
+                }
             )
 
         return True if data else False, data
@@ -462,8 +520,12 @@ class TestDialog(QDialog):
             version_manifest = json.loads(path.read_text())
             return version_manifest
         except Exception as e:
-            self.widget_signal.show_error_message.emit(
-                "Unable to read version manifest:\n{}".format(e),
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Cache Error",
+                    "message": "Unable to read version manifest."
+                }
             )
             return None
 
@@ -542,13 +604,17 @@ class TestDialog(QDialog):
                 "Unable to download client while downloading it: {}".format(e.user_message),
             )
         except Exception as e:
-            self.widget_signal.show_error_message.emit(
-                "Unable to download client: {}".format(e),
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Download Error",
+                    "message": "Unable to download client, an unexpected error occurred."
+                }
             )
         finally:
             self.widget_signal.enable_widget.emit(self.button_2)
 
-    def _download_libraries_process(self, ver: str):
+    def _download_libraries(self, ver: str):
         output_dir = Path(self.app.work_dir, "libraries")
         output_dir.mkdir(parents=True, exist_ok=True)
 
@@ -610,13 +676,80 @@ class TestDialog(QDialog):
                 f"{e.user_message}"
             )
         except Exception as e:
-            self.widget_signal.show_error_message.emit(
-                "Unable to collect library artifacts. An unknown error occurred:\n"
-                f"{str(e) + f"\n{type(e)}"}"
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Download Error",
+                    "message": "Unable to collect library artifacts. An unknown error occurred."
+                }
             )
         finally:
             self.widget_signal.enable_widget.emit(self.button_3)
 
+    def _download_assets(self, ver: str):
+        try:
+            self.widget_signal.clean_output.emit()
+
+            ver_data = self.get_cached_version_manifest(ver)
+
+            if not ver_data:
+                return
+
+            _, asset_index, _, _, _, _, _ = find_useful_part_in_specific_version_manifest(ver_data)
+
+            asset_id = asset_index.get("id")
+            assets_dir = Path(self.app.work_dir, "assets")
+            index_path = Path(assets_dir, "indexes", f"{asset_id}.json")
+
+            # Download and save asset manifest
+            asset_manifest = fetch_and_save_asset_manifest(
+                ver_data,
+                index_path,
+            )
+
+            # Download assets files
+            assets, legacy_assets = collect_assets_from_manifest(
+                asset_id,
+                asset_manifest,
+                assets_dir,
+            )
+
+            fails = download_assets_and_copy(
+                assets,
+                legacy_assets,
+                progress_callback=self.download_signal.progress.emit,
+            )
+
+            if fails:
+                self.widget_signal.show_error_message.emit(
+                    "Some assets failed to download:\n"
+                    + "\n".join(file.posix_path for file in fails)
+                )
+            else:
+                self.download_signal.log.emit("All necessary assets were downloaded.")
+        except AssetManifestFetchException as e:
+            self.widget_signal.show_error_message.emit(
+                f"Unable to fetch asset manifest.\n{e.user_message}"
+            )
+        except AssetManifestSaveException as e:
+            self.widget_signal.show_error_message.emit(
+                f"Unable to save asset manifest.\n{e.user_message}"
+            )
+        except AssetDataKeyNotFoundException as e:
+            self.widget_signal.show_error_message.emit(
+                f"Unable to collect assets.\n{e.user_message}"
+            )
+        except Exception as e:
+            self.widget_signal.show_and_print_error_message.emit(
+                {
+                    "error": traceback.format_exception(e),
+                    "title": "Download Error",
+                    "message": "Unable to download assets. An unknown error occurred."
+                }
+            )
+        finally:
+            self.widget_signal.enable_widget.emit(self.button_5)
+
     def redownload_files(self, files: list[FileObject]) -> tuple[bool, list[FileObject]]:
         if not files:
             return True, []