diff --git a/scripts/generate_messages.py b/scripts/generate_messages.py
index ff94dd0..479ab67 100644
--- a/scripts/generate_messages.py
+++ b/scripts/generate_messages.py
@@ -66,6 +66,7 @@ def generate_msg(msg: GameMessageJson) -> None:
         out_file.write('\n')
         out_file.write('from twnet_parser.pretty_print import PrettyPrint\n')
         out_file.write('from twnet_parser.packer import Unpacker\n')
+        out_file.write(get_dependencies(msg))
         out_file.write('\n')
         out_file.write(f'class {name_camel}(PrettyPrint):\n')
         out_file.write('    def __init__(\n')
@@ -113,6 +114,8 @@ def generate_msg(msg: GameMessageJson) -> None:
         out_file.write(',\n'.join(args) + '\n')
         out_file.write('    ) -> None:\n')
         out_file.write(f"        self.message_name = '{name_snake}'\n")
+        out_file.write("        self.system_message = False\n")
+        out_file.write('\n')
         for member in msg['members']:
             # {'name': ['message'], 'type': {'kind': 'string', 'disallow_cc': False}} 
             ftype = 'int'
@@ -178,8 +181,77 @@ def generate_msg(msg: GameMessageJson) -> None:
         out_file.write('        return True\n')
         out_file.write('\n')
         out_file.write('    def pack(self) -> bytes:\n')
-        out_file.write("        return b'todo'\n")
+        out_file.write(gen_pack_return(msg))
 
+def get_dependencies(msg: GameMessageJson) -> str:
+    packer_deps: list[str] = []
+    for member in msg['members']:
+        if member['type']['kind'] == 'string': # TODO: sanitize cc
+            packer_deps.append('pack_str')
+        elif member['type']['kind'] == 'raw':
+            pass
+        # {"name": ["mode"], "type": {"kind": "enum", "enum": ["chat"]}},
+        elif member['type']['kind'] == 'enum':
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] in ('int32', 'tick'):
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] == 'boolean':
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] == 'tune_param': # TODO: think about tune params
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] == 'snapshot_object':
+            # TODO: think about snapshot_object
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] == 'array': # TODO: think about array
+            packer_deps.append('pack_int')
+        elif member['type']['kind'] == 'flags': # TODO: think about flags
+            packer_deps.append('pack_int')
+        else:
+            print(f"Error: unknown type {member['type']}")
+            exit(1)
+    if len(packer_deps) == 0:
+        return ''
+    return 'from twnet_parser.packer import ' + \
+        ', '.join(set(packer_deps)) + '\n'
+
+def pack_field(member: GameMessageMemberJson) -> str:
+    name: str = name_to_snake(member["name"])
+    packer = 'int'
+    if member['type']['kind'] == 'string': # TODO: sanitize cc
+        packer = 'str'
+    elif member['type']['kind'] == 'raw':
+        return f'self.{name}'
+    # {"name": ["mode"], "type": {"kind": "enum", "enum": ["chat"]}},
+    elif member['type']['kind'] == 'enum':
+        packer = 'int'
+    elif member['type']['kind'] in ('int32', 'tick'):
+        packer = 'int'
+    elif member['type']['kind'] == 'boolean':
+        packer = 'int'
+    elif member['type']['kind'] == 'tune_param': # TODO: think about tune params
+        packer = 'int'
+    elif member['type']['kind'] == 'snapshot_object':
+        # TODO: think about snapshot_object
+        packer = 'int'
+    elif member['type']['kind'] == 'array': # TODO: think about array
+        packer = 'int'
+    elif member['type']['kind'] == 'flags': # TODO: think about flags
+        packer = 'int'
+    else:
+        print(f"Error: unknown type {member['type']}")
+        exit(1)
+    return f'pack_{packer}(self.{name})'
+
+def gen_pack_return(msg: GameMessageJson) -> str:
+    members: list[GameMessageMemberJson] = msg['members']
+    if len(members) == 0:
+        return "        return b''"
+    if len(members) == 1:
+        return f'        return {pack_field(members[0])}'
+    mem_strs: list[str] = [
+            f'            {pack_field(member)}' for member in members[1:]]
+    return f"        return {pack_field(members[0])} + \\\n" + \
+            ' + \\\n'.join(mem_strs)
 
 def generate(spec: str) -> None:
     print(f"generating classes from {spec} ...")
diff --git a/twnet_parser/message_parser.py b/twnet_parser/message_parser.py
index 01adb07..3b3095a 100644
--- a/twnet_parser/message_parser.py
+++ b/twnet_parser/message_parser.py
@@ -10,6 +10,7 @@ from twnet_parser.chunk_header import ChunkHeader
 class TodoMessage():
     def __init__(self, name: str) -> None:
         self.message_name = name
+        self.system_message = False
         self.header: ChunkHeader
     def unpack(self, data: bytes) -> bool:
         return len(data) > 0
diff --git a/twnet_parser/net_message.py b/twnet_parser/net_message.py
index 26c20d3..d212c07 100644
--- a/twnet_parser/net_message.py
+++ b/twnet_parser/net_message.py
@@ -4,6 +4,7 @@ from twnet_parser.chunk_header import ChunkHeader
 
 class NetMessage(Protocol):
     message_name: str
+    system_message: bool
     header: ChunkHeader
     def unpack(self, data: bytes) -> bool:
         ...