diff --git a/richka/__init__.py b/richka/__init__.py
index d085c3a..7b0bb48 100644
--- a/richka/__init__.py
+++ b/richka/__init__.py
@@ -1 +1,2 @@
-from .config import *
\ No newline at end of file
+from .config import *
+from .core import *
\ No newline at end of file
diff --git a/richka/__main__.py b/richka/__main__.py
index e69de29..8b13789 100644
--- a/richka/__main__.py
+++ b/richka/__main__.py
@@ -0,0 +1 @@
+
diff --git a/richka/__version__.py b/richka/__version__.py
index 8a6a77f..a68acbb 100644
--- a/richka/__version__.py
+++ b/richka/__version__.py
@@ -5,4 +5,4 @@ __version__ = '0.0.1'
 __author__ = "Ian Xia"
 __author_email__ = "xia@ghink.net"
 __license__ = "MIT"
-__copyright__ = "Copyright Ian Xia"
\ No newline at end of file
+__copyright__ = "Copyright Ian Xia"
diff --git a/richka/config.py b/richka/config.py
index cb5a0d9..eaeaebf 100644
--- a/richka/config.py
+++ b/richka/config.py
@@ -1,13 +1,45 @@
 import richka
 
+import logging
+
 __VERSION = ("Alpha", 0, 0, 1)
 USER_AGENT = f"Richka{__VERSION[0]}/{__VERSION[1]}.{__VERSION[2]}.{__VERSION[3]}"
 HEADERS = {"user-agent": USER_AGENT}
+COROUTINE_LIMIT = 10
+SLICE_THRESHOLD = 10 # MiB
+
+logger = logging.getLogger("Richka Engine")
 
 def set_user_agent(user_agent: str) -> None:
+    """
+    Set Public User Agent for HTTP Requests
+    :param user_agent: String
+    :return:
+    """
     richka.USER_AGENT = user_agent
     richka.HEADERS["user-agent"] = user_agent
 
 def set_headers(headers: dict) -> None:
+    """
+    Set Public Headers for HTTP Requests
+    :param headers: Dictionary
+    :return:
+    """
     for key, value in headers.items():
-        richka.HEADERS[key.lower()] = value
\ No newline at end of file
+        richka.HEADERS[key.lower()] = value
+
+def set_coroutine_limit(coroutine_limit: int) -> None:
+    """
+    Set Coroutine Limit for HTTP Requests
+    :param coroutine_limit: Integer
+    :return:
+    """
+    richka.COROUTINE_LIMIT = coroutine_limit
+
+def set_slice_threshold(slice_threshold: int) -> None:
+    """
+    Set Slice Threshold for HTTP Requests
+    :param slice_threshold: Integer
+    :return:
+    """
+    richka.SLICE_THRESHOLD = slice_threshold
diff --git a/richka/core.py b/richka/core.py
index e69de29..391d8bc 100644
--- a/richka/core.py
+++ b/richka/core.py
@@ -0,0 +1,74 @@
+import time
+import asyncio
+
+import richka
+
+import aiohttp
+
+async def __download_range(session: aiohttp.ClientSession, url: str, start: int, end: int, destination: str) -> None:
+    richka.logger.info(f'Downloading part {start}-{end} of {url} to {destination}.')
+
+    headers = {**richka.HEADERS, **{'range': f'bytes={start}-{end}'}}
+
+    async with session.get(url, headers=headers) as response:
+        content = await response.read()
+        with open(destination, 'r+b') as f:
+            f.seek(start)
+            f.write(content)
+
+    richka.logger.info(f'Downloaded part {start}-{end} of {destination}.')
+
+async def __download_single(session: aiohttp.ClientSession, url: str, destination: str) -> None:
+    richka.logger.info(f'Downloading {url} to {destination}.')
+
+    async with session.get(url, headers=richka.HEADERS) as response:
+        content = await response.read()
+        with open(destination, 'r+b') as f:
+            f.write(content)
+
+    richka.logger.info(f'Downloaded {url} to {destination}.')
+
+async def download(url: str, destination: str) -> float:
+    async with aiohttp.ClientSession() as session:
+        # Get file size
+        async with session.head(url) as response:
+            file_size = int(response.headers.get('Content-Length', 0))
+
+        if not file_size or file_size / pow(1024, 2) <= 10:
+            if not file_size:
+                richka.logger.info(f'Failed to get file size, directly downloading {url}.')
+            else:
+                richka.logger.info(f"Downloading {url} ({file_size}) to {destination} with signle mode.")
+
+            # Create an empty file
+            with open(destination, 'wb') as f:
+                f.truncate(file_size)
+
+            # Start task
+            start_time = time.time()
+            await __download_single(session, url, destination)
+            end_time = time.time()
+            return end_time - start_time
+
+        richka.logger.info(f'Downloading {url} ({file_size}) to {destination} with slicing mode.')
+
+        # Calc slice size
+        part_size = file_size // richka.COROUTINE_LIMIT
+
+        # Create an empty file
+        with open(destination, 'wb') as f:
+            f.truncate(file_size)
+
+        # Create coroutine tasks
+        tasks = []
+        for i in range(richka.COROUTINE_LIMIT):
+            start = i * part_size
+            end = (start + part_size - 1) if i < richka.COROUTINE_LIMIT - 1 else (file_size - 1)
+            task = __download_range(session, url, start, end, destination)
+            tasks.append(task)
+
+        # Start all task
+        start_time = time.time()
+        await asyncio.gather(*tasks)
+        end_time = time.time()
+        return end_time - start_time
\ No newline at end of file
diff --git a/setup.py b/setup.py
index 181ca3b..683e8d4 100644
--- a/setup.py
+++ b/setup.py
@@ -39,4 +39,4 @@ setup(
     },
     package_data={'': ['README.md']},
     include_package_data=True,
-    zip_safe=False)
\ No newline at end of file
+    zip_safe=False)