diff --git a/lua/client/client.lua b/lua/client/client.lua
index 8e2901be..c8aff3e9 100644
--- a/lua/client/client.lua
+++ b/lua/client/client.lua
@@ -3,15 +3,15 @@ Client = class('Client')
 -- load client classes
 ClientPlayer = require "client.clientplayer"
 
-freekill.client_callback = {}
+fk.client_callback = {}
 
 function Client:initialize()
-    self.client = freekill.ClientInstance
+    self.client = fk.ClientInstance
     self.notifyUI = function(self, command, jsonData)
-        freekill.Backend:emitNotifyUI(command, jsonData)
+        fk.Backend:emitNotifyUI(command, jsonData)
     end
     self.client.callback = function(_self, command, jsonData)
-        local cb = freekill.client_callback[command]
+        local cb = fk.client_callback[command]
         if (type(cb) == "function") then
             cb(jsonData)
         else
@@ -22,31 +22,31 @@ function Client:initialize()
     self.players = {}       -- ClientPlayer[]
 end
 
-freekill.client_callback["Setup"] = function(jsonData)
+fk.client_callback["Setup"] = function(jsonData)
     -- jsonData: [ int id, string screenName, string avatar ]
     local data = json.decode(jsonData)
     local id, name, avatar = data[1], data[2], data[3]
-    local self = freekill.Self
+    local self = fk.Self
     self:setId(id)
     self:setScreenName(name)
     self:setAvatar(avatar)
 end
 
-freekill.client_callback["AddPlayer"] = function(jsonData)
+fk.client_callback["AddPlayer"] = function(jsonData)
     -- jsonData: [ int id, string screenName, string avatar ]
     -- when other player enter the room, we create clientplayer(C and lua) for them
     local data = json.decode(jsonData)
     local id, name, avatar = data[1], data[2], data[3]
-    local player = freekill.ClientInstance:addPlayer(id, name, avatar)
+    local player = fk.ClientInstance:addPlayer(id, name, avatar)
     table.insert(ClientInstance.players, ClientPlayer:new(player))
     ClientInstance:notifyUI("AddPlayer", jsonData)
 end
 
-freekill.client_callback["RemovePlayer"] = function(jsonData)
+fk.client_callback["RemovePlayer"] = function(jsonData)
     -- jsonData: [ int id ]
     local data = json.decode(jsonData)
     local id = data[1]
-    freekill.ClientInstance:removePlayer(id)
+    fk.ClientInstance:removePlayer(id)
     for _, p in ipairs(ClientInstance.players) do
         if p.player:getId() == id then
             table.removeOne(ClientInstance.players, p)
@@ -56,7 +56,7 @@ freekill.client_callback["RemovePlayer"] = function(jsonData)
     ClientInstance:notifyUI("RemovePlayer", jsonData)
 end
 
-freekill.client_callback["ArrangeSeats"] = function(jsonData)
+fk.client_callback["ArrangeSeats"] = function(jsonData)
     local data = json.decode(jsonData)
     local n = #ClientInstance.players
     local players = {}
diff --git a/lua/core/card.lua b/lua/core/card.lua
index 408829b0..7d8e755f 100644
--- a/lua/core/card.lua
+++ b/lua/core/card.lua
@@ -1,37 +1,55 @@
-local SUITS = {
-  "Spade",
-  "Club",
-  "Diamond",
-  "Heart",
-  "NonSuit",
-}
-
-CardSuit = Util:createEnum(SUITS)
-
-local COLOR = {
-  "Red",
-  "Black",
-  "NonColor",
-}
-
-CardColor = Util:createEnum(COLOR)
-
+---@class Card : Object
+---@field package Package
+---@field name string
+---@field suit number # enum suit
+---@field number number
+---@field color number # enum color
+---@field id number
+---@field type number # enum type
 local Card = class("Card")
 
-function Card:initialize(name, suit, cardNumber)
-  self.name = name
-  self.suit = suit
-  self.cardNumber = cardNumber
-end
+-- enum Suit
+fk.createEnum(Card, {
+    "Spade",
+    "Club",
+    "Heart",
+    "Diamond",
+    "NoSuit"
+})
 
-function Card:getColor()
-  if self.suit == CardSuit.Spade or self.suit == CardSuit.Club then
-    return CardColor.Red
-  elseif self.suit == CardSuit.Diamond or self.suit == CardSuit.Heart then
-    return CardColor.Black
-  else
-    return CardColor.NonColor
-  end
+-- enum Color
+fk.createEnum(Card, {
+    "Black",
+    "Red",
+    "NoColor"
+})
+
+-- enum Type
+fk.createEnum(Card, {
+    "TypeSkill",
+    "TypeBasic",
+    "TypeTrick",
+    "TypeEquip"
+})
+
+function Card:initialize(name, suit, number, color)
+    self.name = name
+    self.suit = suit or Card.NoSuit
+    self.number = number or 0
+
+    if suit == Card.Spade or suit == Card.Club then
+        self.color = Card.Black
+    elseif suit == Card.Heart or suit == Card.Diamond then
+        self.color = Card.Red
+    elseif color ~= nil then
+        self.color = color
+    else
+        self.color = Card.NoColor
+    end
+
+    self.package = nil
+    self.id = 0
+    self.type = 0
 end
 
 return Card
diff --git a/lua/core/card_type/basic.lua b/lua/core/card_type/basic.lua
new file mode 100644
index 00000000..87dd0952
--- /dev/null
+++ b/lua/core/card_type/basic.lua
@@ -0,0 +1,9 @@
+---@class BasicCard : Card
+local BasicCard = Card:subclass("BasicCard")
+
+function BasicCard:initialize(name, suit, number)
+    Card.initialize(self, name, suit, number)
+    self.type = Card.TypeBasic
+end
+
+return BasicCard
diff --git a/lua/core/card_type/equip.lua b/lua/core/card_type/equip.lua
new file mode 100644
index 00000000..d971ddd4
--- /dev/null
+++ b/lua/core/card_type/equip.lua
@@ -0,0 +1,9 @@
+---@class EquipCard : Card
+local EquipCard = Card:subclass("EquipCard")
+
+function EquipCard:initialize(name, suit, number)
+    Card.initialize(self, name, suit, number)
+    self.type = Card.TypeEquip
+end
+
+return EquipCard
diff --git a/lua/core/card_type/skill.lua b/lua/core/card_type/skill.lua
new file mode 100644
index 00000000..a3064d13
--- /dev/null
+++ b/lua/core/card_type/skill.lua
@@ -0,0 +1,9 @@
+---@class SkillCard : Card
+local SkillCard = Card:subclass("SkillCard")
+
+function SkillCard:initialize(name)
+    Card.initialize(self, name, Card.NoSuit, 0)
+    self.type = Card.TypeSkill
+end
+
+return SkillCard
diff --git a/lua/core/card_type/trick.lua b/lua/core/card_type/trick.lua
new file mode 100644
index 00000000..ce91a5fd
--- /dev/null
+++ b/lua/core/card_type/trick.lua
@@ -0,0 +1,9 @@
+---@class TrickCard : Card
+local TrickCard = Card:subclass("TrickCard")
+
+function TrickCard:initialize(name, suit, number)
+    Card.initialize(self, name, suit, number)
+    self.type = Card.TypeTrick
+end
+
+return TrickCard
diff --git a/lua/core/engine.lua b/lua/core/engine.lua
index eb88a399..1c41443d 100644
--- a/lua/core/engine.lua
+++ b/lua/core/engine.lua
@@ -46,14 +46,11 @@ function Engine:loadPackage(pack)
 end
 
 function Engine:loadPackages()
-    assert(FileIO.isDir("packages"))
-    FileIO.cd("packages")
-    for _, dir in ipairs(FileIO.ls()) do
-        if FileIO.isDir(dir) then
-            self:loadPackage(require(dir))
+    for _, dir in ipairs(FileIO.ls("packages")) do
+        if FileIO.isDir("packages/" .. dir) then
+            self:loadPackage(require(string.format("packages.%s", dir)))
         end
     end
-    FileIO.cd("..")
 end
 
 ---@param t table
@@ -98,13 +95,17 @@ function Engine:addGenerals(generals)
     end
 end
 
+local cardId = 1
+---@param card Card
 function Engine:addCard(card)
     assert(card.class:isSubclassOf(Card))
+    card.id = cardId
+    cardId = cardId + 1
     table.insert(self.cards, card)
 end
 
+---@param cards Card[]
 function Engine:addCards(cards)
-    assert(type(cards) == "table")
     for _, card in ipairs(cards) do
         self:addCard(card)
     end
diff --git a/lua/core/general.lua b/lua/core/general.lua
index 4c3f68b7..552bfa6d 100644
--- a/lua/core/general.lua
+++ b/lua/core/general.lua
@@ -1,9 +1,19 @@
---- @class General : Object
+---@class General : Object
+---@field package Package
+---@field name string
+---@field kingdom string
+---@field hp number
+---@field maxHp number
+---@field gender number
+---@field skills table
+---@field other_skills table
 General = class("General")
 
 -- enum Gender
-General.Male = 0
-General.Female = 1
+fk.createEnum(General, {
+    "Male",
+    "Female"
+})
 
 function General:initialize(package, name, kingdom, hp, maxHp, gender, initialHp)
     self.package = package
@@ -12,7 +22,6 @@ function General:initialize(package, name, kingdom, hp, maxHp, gender, initialHp
     self.hp = hp
     self.maxHp = maxHp or hp
     self.gender = gender or General.Male
-    self.initialHp = initialHp or maxHp
 
     self.skills = {}        -- Skill[]
     -- skill belongs other general, e.g. "mashu" of pangde
diff --git a/lua/core/package.lua b/lua/core/package.lua
index aa1c5700..b131431b 100644
--- a/lua/core/package.lua
+++ b/lua/core/package.lua
@@ -8,9 +8,11 @@
 local Package = class("Package")
 
 -- enum Type
-Package.GeneralPack = 0
-Package.CardPack = 1
-Package.SpecialPack = 2
+fk.createEnum(Package, {
+    "GeneralPack",
+    "CardPack",
+    "SpecialPack"
+})
 
 function Package:initialize(name, _type)
     assert(type(name) == "string")
@@ -45,4 +47,18 @@ function Package:addGeneral(general)
     table.insert(self.generals, general)
 end
 
+---@param card Card
+function Package:addCard(card)
+    assert(card.class and card:isInstanceOf(Card))
+    card.package = self
+    table.insert(self.cards, card)
+end
+
+---@param cards Card[]
+function Package:addCards(cards)
+    for _, card in ipairs(cards) do
+        self:addCard(card)
+    end
+end
+
 return Package
diff --git a/lua/core/player.lua b/lua/core/player.lua
index d6c188fb..10ae4e0c 100644
--- a/lua/core/player.lua
+++ b/lua/core/player.lua
@@ -19,11 +19,14 @@ function Player:initialize()
     self.playerSkills = {}
 end
 
+---@param general General
+---@param setHp boolean
+---@param addSkills boolean
 function Player:setGeneral(general, setHp, addSkills)
     self.general = general
     if setHp then
         self.maxHp = general.maxHp
-        self.hp = general.initialHp
+        self.hp = general.hp
     end
 
     if addSkills then
@@ -31,9 +34,4 @@ function Player:setGeneral(general, setHp, addSkills)
     end
 end
 
-function Player:setHp(maxHp, initialHp)
-    self.maxHp = maxHp
-    self.hp = initialHp or maxHp
-end
-
 return Player
diff --git a/lua/core/skill.lua b/lua/core/skill.lua
index 0f393a20..39814185 100644
--- a/lua/core/skill.lua
+++ b/lua/core/skill.lua
@@ -1,15 +1,13 @@
-local SKILL_TYPE = {
+---@class Skill
+local Skill = class("Skill")
+
+fk.createEnum(Skill, {
     "Common",
     "Frequent",
     "Compulsory",
     "Awaken",
     "Limit",
-    "Lord",
-}
-
-SkillType = Util:createEnum(SKILL_TYPE)
-
-local Skill = class("Skill")
+})
 
 function Skill:initialize(name, skillType)
     self.name = name
diff --git a/lua/core/util.lua b/lua/core/util.lua
index fa9e27d3..55112469 100644
--- a/lua/core/util.lua
+++ b/lua/core/util.lua
@@ -5,7 +5,7 @@ local qlist_iterator = function(list, n)
 	end
 end
 
-function freekill.qlist(list)
+function fk.qlist(list)
 	return qlist_iterator, list, -1
 end
 
@@ -33,46 +33,47 @@ end
 Sql = {
 	---@param filename string
 	open = function(filename)
-		return freekill.OpenDatabase(filename)
+		return fk.OpenDatabase(filename)
 	end,
 
-	---@param db freekill.SQLite3
+	---@param db fk.SQLite3
 	close = function(db)
-		freekill.CloseDatabase(db)
+		fk.CloseDatabase(db)
 	end,
 
 	--- Execute an SQL statement.
-	---@param db freekill.SQLite3
+	---@param db fk.SQLite3
 	---@param sql string
 	exec = function(db, sql)
-		freekill.ExecSQL(db, sql)
+		fk.ExecSQL(db, sql)
 	end,
 
 	--- Execute a `SELECT` SQL statement.
-	---@param db freekill.SQLite3
+	---@param db fk.SQLite3
 	---@param sql string
 	---@return table data # { [columnName] --> result : string[] }
 	exec_select = function(db, sql)
-		return json.decode(freekill.SelectFromDb(db, sql))
+		return json.decode(fk.SelectFromDb(db, sql))
 	end,
 }
 
 FileIO = {
-	pwd = freekill.QmlBackend_pwd,
+	pwd = fk.QmlBackend_pwd,
 	ls = function(filename)
 		if filename == nil then
-			return freekill.QmlBackend_ls(".")
+			return fk.QmlBackend_ls(".")
 		else
-			return freekill.QmlBackend_ls(filename)
+			return fk.QmlBackend_ls(filename)
 		end
 	end,
-	cd = freekill.QmlBackend_cd,
-	exists = freekill.QmlBackend_exists,
-	isDir = freekill.QmlBackend_isDir
+	cd = fk.QmlBackend_cd,
+	exists = fk.QmlBackend_exists,
+	isDir = fk.QmlBackend_isDir
 }
 
-os.getms = freekill.GetMicroSecond
+os.getms = fk.GetMicroSecond
 
+---@class Stack : Object
 Stack = class("Stack")
 function Stack:initialize()
 	self.t = {}
@@ -106,16 +107,11 @@ function table:removeOne(element)
 	return false
 end
 
-local Util = class("Util")
-
-function Util.static:createEnum(tbl, index)
-  assert(type(tbl) == "table")
-  local enumtbl = {}
-  local enumindex = index or 0
-  for i, v in ipairs(tbl) do
-      enumtbl[v] = enumindex + i
-  end
-  return enumtbl
+--- convert a table to enum, e.g. core/card.lua
+---@param table table # class to store the enum
+---@param enum string[]
+function fk.createEnum(table, enum)
+	for i, v in ipairs(enum) do
+		table[v] = i
+	end
 end
-
-return Util
diff --git a/lua/fk_ex.lua b/lua/fk_ex.lua
new file mode 100644
index 00000000..4b7ab487
--- /dev/null
+++ b/lua/fk_ex.lua
@@ -0,0 +1,38 @@
+---@param spec table
+---@return BasicCard
+function fk.CreateBasicCard(spec)
+    assert(type(spec.name) == "string" or type(spec.class_name) == "string")
+	if not spec.name then spec.name = spec.class_name
+	elseif not spec.class_name then spec.class_name = spec.name end
+	if spec.suit then assert(type(spec.suit) == "number") end
+	if spec.number then assert(type(spec.number) == "number") end
+
+    local card = BasicCard:new(spec.name, spec.suit, spec.number)
+    return card
+end
+
+---@param spec table
+---@return TrickCard
+function fk.CreateTrickCard(spec)
+    assert(type(spec.name) == "string" or type(spec.class_name) == "string")
+	if not spec.name then spec.name = spec.class_name
+	elseif not spec.class_name then spec.class_name = spec.name end
+	if spec.suit then assert(type(spec.suit) == "number") end
+	if spec.number then assert(type(spec.number) == "number") end
+
+    local card = TrickCard:new(spec.name, spec.suit, spec.number)
+    return card
+end
+
+---@param spec table
+---@return EquipCard
+function fk.CreateEquipCard(spec)
+    assert(type(spec.name) == "string" or type(spec.class_name) == "string")
+	if not spec.name then spec.name = spec.class_name
+	elseif not spec.class_name then spec.class_name = spec.name end
+	if spec.suit then assert(type(spec.suit) == "number") end
+	if spec.number then assert(type(spec.number) == "number") end
+
+    local card = EquipCard:new(spec.name, spec.suit, spec.number)
+    return card
+end
diff --git a/lua/freekill.lua b/lua/freekill.lua
index faa7a3f9..b2f17c49 100644
--- a/lua/freekill.lua
+++ b/lua/freekill.lua
@@ -6,14 +6,12 @@ package.path = package.path .. ";./lua/lib/?.lua"
 
 -- load libraries
 
----@type class
 class = require "middleclass"
-
----@type json
 json = require "json"
 
-require "sha256"
-Util = require "core.util"
+dofile "lua/lib/sha256.lua"
+dofile "lua/core/util.lua"
+
 math.randomseed(os.time())
 
 DebugMode = true
@@ -29,8 +27,13 @@ Engine = require "core.engine"
 Package = require "core.package"
 General = require "core.general"
 Card = require "core.card"
+SkillCard = require "core.card_type.skill"
+BasicCard = require "core.card_type.basic"
+TrickCard = require "core.card_type.trick"
+EquipCard = require "core.card_type.equip"
 Skill = require "core.skill"
 Player = require "core.player"
 
 -- load packages
+dofile "lua/fk_ex.lua"
 Fk = Engine:new()
diff --git a/lua/server/gamelogic.lua b/lua/server/gamelogic.lua
index 551e6af2..f50921f0 100644
--- a/lua/server/gamelogic.lua
+++ b/lua/server/gamelogic.lua
@@ -1,4 +1,9 @@
 ---@class GameLogic: Object
+---@field room Room
+---@field skill_table table
+---@filed skills table
+---@field event_stack Stack
+---@field role_table table
 local GameLogic = class("GameLogic")
 
 function GameLogic:initialize(room)
diff --git a/lua/server/room.lua b/lua/server/room.lua
index 00718af8..82c84fdd 100644
--- a/lua/server/room.lua
+++ b/lua/server/room.lua
@@ -1,8 +1,15 @@
 ---@class Room : Object
+---@field room fk.Room
+---@field server Server
+---@field players table
+---@field alive_players table
+---@field game_finished boolean
+---@field timeout number
 local Room = class("Room")
 
 function Room:initialize(_room)
     self.room = _room
+    self.server = nil
     self.players = {}       -- ServerPlayer[]
     self.alive_players = {}
     self.game_finished = false
@@ -11,7 +18,7 @@ end
 
 -- When this function returns, the Room(C++) thread stopped.
 function Room:run()
-    for _, p in freekill.qlist(self.room:getPlayers()) do
+    for _, p in fk.qlist(self.room:getPlayers()) do
         local player = ServerPlayer:new(p)
         player.state = p:getStateString()
         player.room = self
@@ -23,12 +30,17 @@ function Room:run()
     self.logic:run()
 end
 
+---@param player ServerPlayer
+---@param property string
 function Room:broadcastProperty(player, property)
     for _, p in ipairs(self.players) do
         self:notifyProperty(p, player, property)
     end
 end
 
+---@param p ServerPlayer
+---@param player ServerPlayer
+---@param property string
 function Room:notifyProperty(p, player, property)
     p:doNotify("PropertyUpdate", json.encode{
         player:getId(),
@@ -37,15 +49,23 @@ function Room:notifyProperty(p, player, property)
     })
 end
 
+---@param command string
+---@param jsonData string
+---@param players ServerPlayer[] # default all players
 function Room:doBroadcastNotify(command, jsonData, players)
     players = players or self.players
-    local tolist = freekill.SPlayerList()
+    local tolist = fk.SPlayerList()
     for _, p in ipairs(players) do
         tolist:append(p.serverplayer)
     end
     self.room:doBroadcastNotify(tolist, command, jsonData)
 end
 
+---@param player ServerPlayer
+---@param command string
+---@param jsonData string
+---@param wait boolean # default true
+---@return string | nil
 function Room:doRequest(player, command, jsonData, wait)
     if wait == nil then wait = true end
     player:doRequest(command, jsonData, self.timeout)
@@ -55,6 +75,8 @@ function Room:doRequest(player, command, jsonData, wait)
     end
 end
 
+---@param command string
+---@param players ServerPlayer[]
 function Room:doBroadcastRequest(command, players)
     players = players or self.players
     self:notifyMoveFocus(players, command)
@@ -72,6 +94,8 @@ function Room:doBroadcastRequest(command, players)
     end
 end
 
+---@param players ServerPlayer | ServerPlayer[]
+---@param command string
 function Room:notifyMoveFocus(players, command)
     if (players.class) then
         players = {players}
@@ -116,6 +140,7 @@ function Room:adjustSeats()
     self:doBroadcastNotify("ArrangeSeats", json.encode(player_circle))
 end
 
+---@return ServerPlayer | nil
 function Room:getLord()
     local lord = self.players[1]
     if lord.role == "lord" then return lord end
@@ -126,12 +151,17 @@ function Room:getLord()
     return nil
 end
 
+---@param expect ServerPlayer
+---@return ServerPlayer[]
 function Room:getOtherPlayers(expect)
     local ret = {table.unpack(self.players)}
     table.removeOne(ret, expect)
     return ret
 end
 
+---@param player ServerPlayer
+---@param generals string[]
+---@return string
 function Room:askForGeneral(player, generals)
     local command = "AskForGeneral"
     self:notifyMoveFocus(player, command)
diff --git a/lua/server/server.lua b/lua/server/server.lua
index 6c953b7d..50715f1b 100644
--- a/lua/server/server.lua
+++ b/lua/server/server.lua
@@ -1,4 +1,8 @@
 ---@class Server : Object
+---@field server fk.Server
+---@field db fk.SQLite3
+---@field rooms table
+---@field players table
 Server = class('Server')
 
 -- load server classes
@@ -6,13 +10,13 @@ Room = require "server.room"
 GameLogic = require "server.gamelogic"
 ServerPlayer = require "server.serverplayer"
 
-freekill.server_callback = {}
+fk.server_callback = {}
 
 function Server:initialize()
-    self.server = freekill.ServerInstance
-    self.db = freekill.ServerInstance:getDatabase()
+    self.server = fk.ServerInstance
+    self.db = fk.ServerInstance:getDatabase()
     self.server.callback = function(_self, command, jsonData)
-        local cb = freekill.server_callback[command]
+        local cb = fk.server_callback[command]
         if (type(cb) == "function") then
             cb(jsonData)
         else
@@ -37,18 +41,18 @@ function Server:initialize()
     self.players = {}   -- id --> ServerPlayer
 end
 
-freekill.server_callback["UpdateAvatar"] = function(jsonData)
+fk.server_callback["UpdateAvatar"] = function(jsonData)
     -- jsonData: [ int uid, string newavatar ]
     local data = json.decode(jsonData)
     local id, avatar = data[1], data[2]
     local sql = "UPDATE userinfo SET avatar='%s' WHERE id=%d;"
     Sql.exec(ServerInstance.db, string.format(sql, avatar, id))
-    local player = freekill.ServerInstance:findPlayer(id)
+    local player = fk.ServerInstance:findPlayer(id)
     player:setAvatar(avatar)
     player:doNotify("UpdateAvatar", avatar)
 end
 
-freekill.server_callback["UpdatePassword"] = function(jsonData)
+fk.server_callback["UpdatePassword"] = function(jsonData)
     -- jsonData: [ int uid, string oldpassword, int newpassword ]
     local data = json.decode(jsonData)
     local id, old, new = data[1], data[2], data[3]
@@ -63,38 +67,38 @@ freekill.server_callback["UpdatePassword"] = function(jsonData)
         Sql.exec(db, string.format(sql_update, sha256(new), id))
     end
 
-    local player = freekill.ServerInstance:findPlayer(tonumber(id))
+    local player = fk.ServerInstance:findPlayer(tonumber(id))
     player:doNotify("UpdatePassword", passed and "1" or "0")
 end
 
-freekill.server_callback["CreateRoom"] = function(jsonData)
+fk.server_callback["CreateRoom"] = function(jsonData)
     -- jsonData: [ int uid, string name, int capacity ]
     local data = json.decode(jsonData)
-    local owner = freekill.ServerInstance:findPlayer(tonumber(data[1]))
+    local owner = fk.ServerInstance:findPlayer(tonumber(data[1]))
     local roomName = data[2]
     local capacity = data[3]
-    freekill.ServerInstance:createRoom(owner, roomName, capacity)
+    fk.ServerInstance:createRoom(owner, roomName, capacity)
 end
 
-freekill.server_callback["EnterRoom"] = function(jsonData)
+fk.server_callback["EnterRoom"] = function(jsonData)
     -- jsonData: [ int uid, int roomId ]
     local data = json.decode(jsonData)
-    local player = freekill.ServerInstance:findPlayer(tonumber(data[1]))
-    local room = freekill.ServerInstance:findRoom(tonumber(data[2]))
+    local player = fk.ServerInstance:findPlayer(tonumber(data[1]))
+    local room = fk.ServerInstance:findRoom(tonumber(data[2]))
     room:addPlayer(player)
 end
 
-freekill.server_callback["QuitRoom"] = function(jsonData)
+fk.server_callback["QuitRoom"] = function(jsonData)
     -- jsonData: [ int uid ]
     local data = json.decode(jsonData)
-    local player = freekill.ServerInstance:findPlayer(tonumber(data[1]))
+    local player = fk.ServerInstance:findPlayer(tonumber(data[1]))
     local room = player:getRoom()
     if not room:isLobby() then
         room:removePlayer(player)
     end
 end
 
-freekill.server_callback["DoLuaScript"] = function(jsonData)
+fk.server_callback["DoLuaScript"] = function(jsonData)
     -- jsonData: [ int uid, string luaScript ]
     -- warning: only use this in debugging mode.
     if not DebugMode then return end
@@ -102,7 +106,7 @@ freekill.server_callback["DoLuaScript"] = function(jsonData)
     assert(load(data[2]))()
 end
 
-freekill.server_callback["PlayerStateChanged"] = function(jsonData)
+fk.server_callback["PlayerStateChanged"] = function(jsonData)
     -- jsonData: [ int uid, string stateString ]
     -- note: this function is not called by Router.
     local data = json.decode(jsonData)
diff --git a/lua/server/serverplayer.lua b/lua/server/serverplayer.lua
index 3bf61cad..75d67483 100644
--- a/lua/server/serverplayer.lua
+++ b/lua/server/serverplayer.lua
@@ -1,4 +1,11 @@
 ---@class ServerPlayer : Player
+---@field serverplayer fk.ServerPlayer
+---@field room Room
+---@field next ServerPlayer
+---@field request_data string
+---@field client_reply string
+---@field default_reply string
+---@field reply_ready boolean
 local ServerPlayer = Player:subclass("ServerPlayer")
 
 function ServerPlayer:initialize(_self)
@@ -15,14 +22,23 @@ function ServerPlayer:initialize(_self)
     self.reply_ready = false
 end
 
+---@return number
 function ServerPlayer:getId()
     return self.serverplayer:getId()
 end
 
+---@param command string
+---@param jsonData string
 function ServerPlayer:doNotify(command, jsonData)
     self.serverplayer:doNotify(command, jsonData)
 end
 
+--- Send a request to client, and allow client to reply within *timeout* seconds.
+---
+--- *timeout* must not be negative. If nil, room.timeout is used.
+---@param command string
+---@param jsonData string
+---@param timeout number
 function ServerPlayer:doRequest(command, jsonData, timeout)
     timeout = timeout or self.room.timeout
     self.client_reply = ""
@@ -30,6 +46,11 @@ function ServerPlayer:doRequest(command, jsonData, timeout)
     self.serverplayer:doRequest(command, jsonData, timeout)
 end
 
+--- Wait for at most *timeout* seconds for reply from client.
+---
+--- If *timeout* is negative or **nil**, the function will wait forever until get reply.
+---@param timeout number # seconds to wait
+---@return string reply # JSON data
 function ServerPlayer:waitForReply(timeout)
     local result = ""
     if timeout == nil then
diff --git a/lua/vscode/freekill.lua b/lua/vscode/freekill.lua
index b2dd0aa2..ed8e0cef 100644
--- a/lua/vscode/freekill.lua
+++ b/lua/vscode/freekill.lua
@@ -3,23 +3,23 @@
 -- Note: these files are not used by FreeKill.
 -- Just for convenience when using sumneko.lua
 
----@class freekill
+---@class fk
 ---FreeKill's lua API
-freekill = {}
+fk = {}
 
----@class freekill.SPlayerList
+---@class fk.SPlayerList
 SPlayerList = {}
 
 --- * get microsecond from Epoch
 ---@return number microsecond
-function freekill:GetMicroSecond()end
+function fk:GetMicroSecond()end
 
 --- construct a QList<ServerPlayer *>.
----@return freekill.SPlayerList
-function freekill:SPlayerList()end
+---@return fk.SPlayerList
+function fk:SPlayerList()end
 
-function freekill.QmlBackend_pwd()end
-function freekill.QmlBackend_ls(filename)end
-function freekill.QmlBackend_cd(dir)end
-function freekill.QmlBackend_exists(file)end
-function freekill.QmlBackend_isDir(file)end
+function fk.QmlBackend_pwd()end
+function fk.QmlBackend_ls(filename)end
+function fk.QmlBackend_cd(dir)end
+function fk.QmlBackend_exists(file)end
+function fk.QmlBackend_isDir(file)end
diff --git a/lua/vscode/lib.lua b/lua/vscode/lib.lua
index 78d0549b..203a5cc2 100644
--- a/lua/vscode/lib.lua
+++ b/lua/vscode/lib.lua
@@ -20,6 +20,10 @@ function Object:subclass(name)end
 ---@return boolean
 function Object:isInstanceOf(class) end
 
+---@param class class
+---@return boolean
+function Object:isSubclassOf(class) end
+
 ---@class json
 json = {}
 
diff --git a/lua/vscode/player.lua b/lua/vscode/player.lua
index fd99c6d0..22f25b4c 100644
--- a/lua/vscode/player.lua
+++ b/lua/vscode/player.lua
@@ -1,6 +1,6 @@
 ---@meta
 
----@class freekill.Player
+---@class fk.Player
 FPlayer = {}
 
 ---@return number id
@@ -27,16 +27,16 @@ function FPlayer:getStateString()end
 ---@param state string
 function FPlayer:setStateString(state)end
 
----@class freekill.ServerPlayer : freekill.Player
+---@class fk.ServerPlayer : fk.Player
 FServerPlayer = {}
 
----@return freekill.Server
+---@return fk.Server
 function FServerPlayer:getServer()end
 
----@return freekill.Room
+---@return fk.Room
 function FServerPlayer:getRoom()end
 
----@param room freekill.Room
+---@param room fk.Room
 function FServerPlayer:setRoom(room)end
 
 ---@param msg string
diff --git a/lua/vscode/qt.lua b/lua/vscode/qt.lua
index 3cc3b3ef..62a8bdda 100644
--- a/lua/vscode/qt.lua
+++ b/lua/vscode/qt.lua
@@ -3,15 +3,15 @@
 ---@return number length
 function SPlayerList:length()end
 
----@param e freekill.ServerPlayer
+---@param e fk.ServerPlayer
 function SPlayerList:append(e)end
 
----@param e freekill.ServerPlayer
+---@param e fk.ServerPlayer
 ---@return boolean
 function SPlayerList:contains(e)end
 
 ---@param index number
----@return freekill.ServerPlayer | nil
+---@return fk.ServerPlayer | nil
 function SPlayerList:at(index)end
 
 function SPlayerList:first()end
diff --git a/lua/vscode/server.lua b/lua/vscode/server.lua
index be029926..8c96da57 100644
--- a/lua/vscode/server.lua
+++ b/lua/vscode/server.lua
@@ -1,29 +1,29 @@
 ---@meta
 
----@class freekill.Server
+---@class fk.Server
 FServer = {}
 
----@type freekill.Server
-freekill.ServerInstance = {}
+---@type fk.Server
+fk.ServerInstance = {}
 
----@class freekill.Room
+---@class fk.Room
 --- Room (C++)
 FRoom = {}
 
----@param owner freekill.ServerPlayer
+---@param owner fk.ServerPlayer
 ---@param name string
 ---@param capacity number
 function FServer:createRoom(owner,name,capacity)end
 
 ---@param id number
----@return freekill.Room room
+---@return fk.Room room
 function FServer:findRoom(id)end
 
 ---@param id number
----@return freekill.ServerPlayer player
+---@return fk.ServerPlayer player
 function FServer:findPlayer(id)end
 
----@return freekill.SQLite3 db
+---@return fk.SQLite3 db
 function FServer:getDatabase()end
 
 function FRoom:getServer()end
diff --git a/lua/vscode/sqlite.lua b/lua/vscode/sqlite.lua
index a53edab7..4a5b39ce 100644
--- a/lua/vscode/sqlite.lua
+++ b/lua/vscode/sqlite.lua
@@ -1,20 +1,20 @@
 ---@meta
 
----@class freekill.SQLite3
+---@class fk.SQLite3
 SQLite3 = {}
 
 ---@param filename string
----@return freekill.SQLite3
-function freekill.OpenDatabase(filename)end
+---@return fk.SQLite3
+function fk.OpenDatabase(filename)end
 
----@param db freekill.SQLite3
+---@param db fk.SQLite3
 ---@param sql string
 ---@return string jsonData
-function freekill.SelectFromDb(db, sql)end
+function fk.SelectFromDb(db, sql)end
 
----@param db freekill.SQLite3
+---@param db fk.SQLite3
 ---@param sql string
-function freekill.ExecSQL(db, sql)end
+function fk.ExecSQL(db, sql)end
 
----@param db freekill.SQLite3
-function freekill.CloseDatabase(db)end
+---@param db fk.SQLite3
+function fk.CloseDatabase(db)end
diff --git a/packages/standard/init.lua b/packages/standard/init.lua
index bfeb7ecb..867a9710 100644
--- a/packages/standard/init.lua
+++ b/packages/standard/init.lua
@@ -1,5 +1,5 @@
 local extension = Package:new("standard")
-extension.metadata = require "standard.metadata"
+extension.metadata = require "packages.standard.metadata"
 
 Fk:loadTranslationTable{
     ["wei"] = "魏",
diff --git a/packages/standard_cards/init.lua b/packages/standard_cards/init.lua
new file mode 100644
index 00000000..b3faa8e7
--- /dev/null
+++ b/packages/standard_cards/init.lua
@@ -0,0 +1,8 @@
+local extension = Package:new("standard_cards", Package.CardPack)
+extension.metadata = require "packages.standard_cards.metadata"
+
+local slash = fk.CreateBasicCard{
+    name = "slash",
+}
+
+return extension
diff --git a/packages/standard_cards/metadata.lua b/packages/standard_cards/metadata.lua
new file mode 100644
index 00000000..bb56d252
--- /dev/null
+++ b/packages/standard_cards/metadata.lua
@@ -0,0 +1,14 @@
+return {
+    name = "standard_cards",
+    author = "official",
+    description = "",
+    collaborators = {
+        program = {},
+        designer = {},
+        cv = {},
+        illustrator = {},
+    },
+
+    dependencies = {},
+    extra_files = {},
+}
diff --git a/src/core/util.cpp b/src/core/util.cpp
index c8602b76..9daffc9b 100644
--- a/src/core/util.cpp
+++ b/src/core/util.cpp
@@ -1,14 +1,14 @@
 #include "util.h"
 
 extern "C" {
-    int luaopen_freekill(lua_State *);
+    int luaopen_fk(lua_State *);
 }
 
 lua_State *CreateLuaState()
 {
     lua_State *L = luaL_newstate();
     luaL_openlibs(L);
-    luaopen_freekill(L);
+    luaopen_fk(L);
 
     return L;
 }
diff --git a/src/swig/freekill.i b/src/swig/freekill.i
index 95d87efe..80ff9c92 100644
--- a/src/swig/freekill.i
+++ b/src/swig/freekill.i
@@ -1,4 +1,4 @@
-%module freekill
+%module fk
 
 %{
 #include "client.h"