diff --git a/src/scripts/basic.lua b/src/scripts/basic.lua
index 5b2cdbc..cd3b588 100644
--- a/src/scripts/basic.lua
+++ b/src/scripts/basic.lua
@@ -1,21 +1,28 @@
----@diagnostic disable-next-line: lowercase-global
+---@diagnostic disable: lowercase-global
 
-function hello(name)
-  if name ~= nil then
-    io.stderr:write("Hello " .. name .. "\n")
-  else
-    io.stderr:write("Hello nil\n")
+--------------------------------------------------------
+--------------------------------------------------------
+function print(...)
+  local args = { ... }
+  for i, arg in ipairs(args) do
+    io.stderr:write("\x1b[32m[" .. i .. "]\x1b[0m " .. tostring(arg) .. "\n")
   end
 end
 
-function add(a, b)
-  return a + b
+--------------------------------------------------------
+--------------------------------------------------------
+function addUser(username, password)
+  app:addUser({ username = username, password = password })
 end
 
+--------------------------------------------------------
+--------------------------------------------------------
 function getCoords()
   return 1.5, 2.5
 end
 
+--------------------------------------------------------
+--------------------------------------------------------
 config = {
   width = 800,
   height = 600,
diff --git a/src/scripts/types.lua b/src/scripts/types.lua
new file mode 100644
index 0000000..e531719
--- /dev/null
+++ b/src/scripts/types.lua
@@ -0,0 +1,15 @@
+---@class User
+---@field username string
+---@field password string
+
+---@class App
+local App = {}
+
+---@param user User
+function App:addUser(user) end
+
+-- ---@return integer
+-- function App:getUserCount() end
+
+---@type App
+app = app
diff --git a/src/zla.zig b/src/zla.zig
index a6c4dc5..153063c 100644
--- a/src/zla.zig
+++ b/src/zla.zig
@@ -1,6 +1,8 @@
 //! ----------------------------------------------------
 //! ----------------------------------------------------
 
+// TODO: Add proper getTable etc
+
 const std = @import("std");
 const lua = @import("luajit");
 const Self = @This();
@@ -12,6 +14,10 @@ const Self = @This();
 state: *lua.lua_State,
 err: ?[*:0]const u8 = null,
 
+//
+// LIFETIME
+//
+
 /// ----------------------------------------------------
 /// ----------------------------------------------------
 pub fn init() !Self {
@@ -32,7 +38,11 @@ pub fn deinit(self: *Self) void {
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn exec(self: *Self, comptime ReturnType: type, code: []const u8) !ReturnType {
+pub fn exec(
+    self: *Self,
+    comptime ReturnType: type,
+    code: []const u8,
+) !ReturnType {
     if (lua.luaL_loadbuffer(self.state, code.ptr, code.len, "") != 0) {
         return self.luaError();
     }
@@ -41,8 +51,12 @@ pub fn exec(self: *Self, comptime ReturnType: type, code: []const u8) !ReturnTyp
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn execFromFile(self: *Self, comptime ReturnType: type, path: [*:0]const u8) !ReturnType {
-    if (lua.luaL_dofile(self.state, path)) {
+pub fn execFromFile(
+    self: *Self,
+    comptime ReturnType: type,
+    path: []const u8,
+) !ReturnType {
+    if (lua.luaL_dofile(self.state, path.ptr)) {
         return self.luaError();
     }
     if (ReturnType == void) return {};
@@ -55,14 +69,20 @@ pub fn execFromFile(self: *Self, comptime ReturnType: type, path: [*:0]const u8)
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn getGlobal(self: *Self, name: [*:0]const u8) void {
-    lua.lua_getglobal(self.state, name);
+pub fn getGlobal(
+    self: *Self,
+    name: []const u8,
+) void {
+    lua.lua_getglobal(self.state, name.ptr);
 }
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn setGlobal(self: *Self, name: [*:0]const u8) void {
-    lua.lua_setglobal(self.state, name);
+pub fn setGlobal(
+    self: *Self,
+    name: []const u8,
+) void {
+    lua.lua_setglobal(self.state, name.ptr);
 }
 
 //
@@ -71,27 +91,11 @@ pub fn setGlobal(self: *Self, name: [*:0]const u8) void {
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn getTop(self: *Self) c_int {
-    return lua.lua_gettop(self.state);
-}
-
-/// ----------------------------------------------------
-/// ----------------------------------------------------
-pub fn pop(self: *Self, n: c_int) void {
-    lua.lua_settop(self.state, -n - 1);
-}
-
-/// ----------------------------------------------------
-/// ----------------------------------------------------
-pub fn pushNil(self: *Self) void {
-    lua.lua_pushnil(self.state);
-}
-
-/// ----------------------------------------------------
-/// ----------------------------------------------------
-pub fn push(self: *Self, value: anytype) void {
-    const T = @TypeOf(value);
-    switch (@typeInfo(T)) {
+pub fn push(
+    self: *Self,
+    value: anytype,
+) void {
+    switch (@typeInfo(@TypeOf(value))) {
         .void, .null => lua.lua_pushnil(self.state),
         .optional => {
             if (value) |v| {
@@ -117,13 +121,16 @@ pub fn push(self: *Self, value: anytype) void {
                 }
             }
         },
-        else => @compileError("unsupported push type: " ++ @typeName(T)),
+        else => @compileError("unsupported push type: " ++ @typeName(@TypeOf(value))),
     }
 }
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn add(self: *Self, values: anytype) void {
+pub fn pushMany(
+    self: *Self,
+    values: anytype,
+) void {
     inline for (values) |v| {
         self.push(v);
     }
@@ -135,7 +142,26 @@ pub fn add(self: *Self, values: anytype) void {
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn to(self: *Self, comptime T: type, idx: c_int) T {
+pub fn to(
+    self: *Self,
+    comptime T: type,
+    idx: i32,
+) T {
+    // --- INFO ---
+    const info = @typeInfo(T);
+
+    // --- # ---
+    if (info == .@"struct" and !info.@"struct".is_tuple) {
+        var result: T = undefined;
+        inline for (info.@"struct".fields) |field| {
+            lua.lua_getfield(self.state, idx, field.name);
+            @field(result, field.name) = self.to(field.type, -1);
+            lua.lua_pop(self.state, 1);
+        }
+        return result;
+    }
+
+    // --- # ---
     return switch (T) {
         bool => lua.lua_toboolean(self.state, idx) != 0,
         i8, i16, i32, i64, u8, u16, u32, u64 => @intCast(lua.lua_tointeger(self.state, idx)),
@@ -155,7 +181,24 @@ pub fn to(self: *Self, comptime T: type, idx: c_int) T {
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn toOwned(self: *Self, comptime T: type, alloc: std.mem.Allocator, idx: c_int) !T {
+pub fn toUserdata(
+    self: *Self,
+    comptime T: type,
+    idx: i32,
+) T {
+    const ud = lua.lua_touserdata(self.state, idx);
+    const ptr: *T = @ptrCast(@alignCast(ud));
+    return ptr.*;
+}
+
+/// ----------------------------------------------------
+/// ----------------------------------------------------
+pub fn toOwned(
+    self: *Self,
+    comptime T: type,
+    alloc: std.mem.Allocator,
+    idx: i32,
+) !T {
     return switch (T) {
         []const u8 => {
             var len: usize = 0;
@@ -176,8 +219,14 @@ pub fn toOwned(self: *Self, comptime T: type, alloc: std.mem.Allocator, idx: c_i
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-fn readReturn(self: *Self, comptime ReturnType: type) ReturnType {
+fn readReturn(
+    self: *Self,
+    comptime ReturnType: type,
+) ReturnType {
+    // --- # ---
     const info = @typeInfo(ReturnType);
+
+    // --- # ---
     if (info == .@"struct" and info.@"struct".is_tuple) {
         const n: c_int = @intCast(info.@"struct".fields.len);
         var result: ReturnType = undefined;
@@ -187,6 +236,8 @@ fn readReturn(self: *Self, comptime ReturnType: type) ReturnType {
         self.pop(n);
         return result;
     }
+
+    // --- # ---
     const result = self.to(ReturnType, -1);
     self.pop(1);
     return result;
@@ -194,24 +245,49 @@ fn readReturn(self: *Self, comptime ReturnType: type) ReturnType {
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn pcall(self: *Self, comptime ReturnType: type, nargs: u32) !ReturnType {
+pub fn pcall(
+    self: *Self,
+    comptime ReturnType: type,
+    nargs: u32,
+) !ReturnType {
+    // --- # ---
     const nresults: c_int = if (ReturnType == void) 0 else switch (@typeInfo(ReturnType)) {
         .@"struct" => |s| if (s.is_tuple) @intCast(s.fields.len) else @as(c_int, 1),
         else => 1,
     };
+
+    // --- # ---
     if (@as(i32, lua.lua_pcall(self.state, @intCast(nargs), nresults, 0)) != 0) {
         return self.luaError();
     }
+
+    // --- # ---
     if (ReturnType == void) return {};
     return self.readReturn(ReturnType);
 }
 
 /// ----------------------------------------------------
+/// --- ZIG ---
+/// ```zig
+/// try zla.call(void, "print", .{
+///     "Hello World",
+///     "Hello Zig",
+/// });
+/// ```
+/// --- LUA ---
+/// ```lua
+/// function print(...)
+///   local args = { ... }
+///   for i, arg in ipairs(args) do
+///     io.stderr:write("\x1b[32m[" .. i .. "]\x1b[0m " .. tostring(arg) .. "\n")
+///   end
+/// end
+/// ```
 /// ----------------------------------------------------
 pub fn call(
     self: *Self,
     comptime ReturnType: type,
-    name: [*:0]const u8,
+    name: []const u8,
     args: anytype,
 ) !ReturnType {
     self.getGlobal(name);
@@ -221,32 +297,17 @@ pub fn call(
     return self.pcall(ReturnType, args.len);
 }
 
-//
-// TABLES
-//
-
-/// ----------------------------------------------------
-/// ----------------------------------------------------
-pub fn tableGet(self: *Self, idx: c_int, key: anytype) void {
-    self.push(key);
-    lua.lua_gettable(self.state, if (idx < 0) idx - 1 else idx);
-}
-
-/// ----------------------------------------------------
-/// ----------------------------------------------------
-pub fn tableSet(self: *Self, idx: c_int, key: anytype, value: anytype) void {
-    self.push(key);
-    self.push(value);
-    lua.lua_settable(self.state, if (idx < 0) idx - 2 else idx);
-}
-
 //
 // REGISTRATION
 //
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn register(self: *Self, name: [*:0]const u8, comptime func: anytype) void {
+pub fn register(
+    self: *Self,
+    name: []const u8,
+    comptime func: anytype,
+) void {
     const fn_info = @typeInfo(@TypeOf(func)).@"fn";
     const Return = fn_info.return_type orelse void;
 
@@ -270,29 +331,33 @@ pub fn register(self: *Self, name: [*:0]const u8, comptime func: anytype) void {
     };
 
     lua.lua_pushcfunction(self.state, Wrapper.luaFunc);
-    lua.lua_setglobal(self.state, name);
+    lua.lua_setglobal(self.state, name.ptr);
 }
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
 pub fn registerWithCtx(
     self: *Self,
-    name: [*:0]const u8,
+    name: []const u8,
     comptime func: anytype,
     ctx: anytype,
 ) void {
+    // --- # ---
     const CtxType = @TypeOf(ctx);
     const fn_info = @typeInfo(@TypeOf(func)).@"fn";
     const Return = fn_info.return_type orelse void;
 
+    // --- # ---
     const Wrapper = struct {
         fn luaFunc(state: ?*lua.lua_State) callconv(.c) c_int {
             var zl = Self{ .state = state.? };
 
+            // --- # ---
             const ctx_ptr: CtxType = @ptrCast(@alignCast(
                 lua.lua_touserdata(state, lua.lua_upvalueindex(1)),
             ));
 
+            // --- # ---
             const args: std.meta.ArgsTuple(@TypeOf(func)) = args: {
                 var a: std.meta.ArgsTuple(@TypeOf(func)) = undefined;
                 inline for (fn_info.params, 0..) |param, i| {
@@ -305,6 +370,7 @@ pub fn registerWithCtx(
                 break :args a;
             };
 
+            // --- # ---
             const ret = @call(.auto, func, args);
             if (Return == void) return 0;
             zl.push(ret);
@@ -312,19 +378,119 @@ pub fn registerWithCtx(
         }
     };
 
+    // --- # ---
     lua.lua_pushlightuserdata(self.state, @ptrCast(@constCast(ctx)));
     lua.lua_pushcclosure(self.state, Wrapper.luaFunc, 1);
-    lua.lua_setglobal(self.state, name);
+    lua.lua_setglobal(self.state, name.ptr);
 }
 
 /// ----------------------------------------------------
 /// ----------------------------------------------------
-pub fn registerMany(self: *Self, values: anytype) void {
+pub fn registerMany(
+    self: *Self,
+    values: anytype,
+) void {
     inline for (values) |value| {
         self.register(value.name, value.func);
     }
 }
 
+/// ----------------------------------------------------
+/// ----------------------------------------------------
+pub fn pushUserdata(
+    self: *Self,
+    ptr: anytype,
+) void {
+    // --- # ---
+    const info = @typeInfo(@TypeOf(ptr));
+    if (info != .pointer) @compileError("pushUserdata requires a pointer");
+    const T = info.pointer.child;
+
+    // --- # ---
+    const ud = lua.lua_newuserdata(self.state, @sizeOf(@TypeOf(ptr)));
+    const stored: *@TypeOf(ptr) = @ptrCast(@alignCast(ud));
+    stored.* = ptr;
+
+    // --- # ---
+    _ = lua.luaL_newmetatable(self.state, @typeName(T));
+    _ = lua.lua_setmetatable(self.state, -2);
+}
+
+/// ----------------------------------------------------
+/// ----------------------------------------------------
+pub fn registerMethods(
+    self: *Self,
+    comptime T: type,
+    methods: anytype,
+) void {
+    // --- # ---
+    _ = lua.luaL_newmetatable(self.state, @typeName(T));
+    lua.lua_getfield(self.state, -1, "__index");
+    if (lua.lua_isnil(self.state, -1)) {
+        lua.lua_pop(self.state, 1);
+        lua.lua_newtable(self.state);
+        lua.lua_pushvalue(self.state, -1);
+        lua.lua_setfield(self.state, -3, "__index");
+    }
+
+    // --- # ---
+    inline for (methods) |method| {
+        // --- # ---
+        const func = method.func;
+        const fn_info = @typeInfo(@TypeOf(func)).@"fn";
+        const Return = fn_info.return_type orelse void;
+
+        // --- # ---
+        const Wrapper = struct {
+            fn luaFunc(state: ?*lua.lua_State) callconv(.c) c_int {
+                // --- # ---
+                var zl = Self{ .state = state.? };
+                const args: std.meta.ArgsTuple(@TypeOf(func)) = args: {
+                    // --- # ---
+                    var a: std.meta.ArgsTuple(@TypeOf(func)) = undefined;
+
+                    // --- # ---
+                    inline for (fn_info.params, 0..) |param, i| {
+                        if (i == 0) {
+                            a[i] = zl.toUserdata(param.type.?, 1);
+                        } else {
+                            a[i] = zl.to(param.type.?, @intCast(i + 1));
+                        }
+                    }
+
+                    // --- # ---
+                    break :args a;
+                };
+                // --- # ---
+                const ret = @call(.auto, func, args);
+                if (Return == void) return 0;
+                zl.push(ret);
+                return 1;
+            }
+        };
+
+        // --- # ---
+        lua.lua_pushcfunction(self.state, Wrapper.luaFunc);
+        lua.lua_setfield(self.state, -2, method.name);
+    }
+
+    lua.lua_pop(self.state, 2);
+}
+
+/// ----------------------------------------------------
+/// ----------------------------------------------------
+pub fn registerMethod(
+    self: *Self,
+    comptime T: type,
+    name: []const u8,
+    comptime func: anytype,
+) void {
+    self.registerMethods(T, &.{.{
+        .name = name,
+        .func = func,
+    }});
+}
+
 //
 // ERRORS
 //
@@ -353,72 +519,95 @@ fn luaError(self: *Self) error{LuaError} {
 // TESTS
 //
 
-fn spawnEntity(name: []const u8, x: f64, y: f64) void {
-    std.debug.print("spawned '{s}' at ({d:.1}, {d:.1})\n", .{ name, x, y });
-}
-
-const Ctx = struct {
-    counter: i64 = 0,
+const User = struct {
+    username: []const u8,
+    password: []const u8,
 };
 
-fn increment(ctx: *Ctx) i64 {
-    ctx.counter += 1;
-    return ctx.counter;
-}
+const App = struct {
+    users: std.ArrayList(User),
+    alloc: std.mem.Allocator,
+
+    pub fn init(alloc: std.mem.Allocator) App {
+        return .{
+            .users = .empty,
+            .alloc = alloc,
+        };
+    }
+
+    pub fn deinit(self: *App) void {
+        self.users.deinit(self.alloc);
+    }
+
+    pub fn addUser(
+        self: *App,
+        user: User,
+    ) void {
+        self.users.append(
+            self.alloc,
+            user,
+        ) catch unreachable;
+    }
+};
 
 test "exec" {
-    // --- ZLA ---
-    var zl: Self = try .init();
-    defer zl.deinit();
+    // --- DEBUG ---
+    std.debug.print("\x1b[34m<--- EXEC --->\x1b[0m\n", .{});
 
-    // --- REGISTER FUNCTIONS TO LUA ---
-    zl.register("spawnEntity", spawnEntity);
+    // --- ZLA ---
+    var zla: Self = try .init();
+    defer zla.deinit();
 
     // --- EXEC FILE ---
-    // try zl.exec(void, @embedFile("scripts/basic.lua"));
-    try zl.execFromFile(void, "src/scripts/basic.lua");
+    try zla.execFromFile(
+        void,
+        "src/scripts/basic.lua",
+    );
 
     // --- CALL ---
-    try zl.call(void, "hello", .{"World"});
-    try zl.call(void, "hello", .{"World"});
-
-    // --- CALL RETURN ---
-    const sum = try zl.call(i64, "add", .{ @as(i64, 3), @as(i64, 4) });
-    std.debug.print("Result: {}\n", .{sum});
-
-    // --- MULTI RETURN ---
-    const coords = try zl.call(struct { f64, f64 }, "getCoords", .{});
-    std.debug.print("coords: ({d:.1}, {d:.1})\n", .{ coords[0], coords[1] });
-
-    // --- EXEC WITH RETURN ---
-    const val = try zl.exec(i64, "return 6 * 7");
-    try std.testing.expectEqual(@as(i64, 42), val);
+    try zla.call(void, "print", .{
+        "Hello World",
+        "Hello Zig",
+    });
 }
 
-// TODO: Nicer tables / generic
+test "userdata" {
+    // --- DEBUG ---
+    std.debug.print("\x1b[34m<--- USERDATA --->\x1b[0m\n", .{});
 
-// test "tables" {
-//     // --- ZLA ---
-//     var zl = try Self.init();
-//     defer zl.deinit();
-//
-//     var ctx = Ctx{};
-//     zl.registerWithCtx("increment", increment, &ctx);
-//
-//     // --- TABLE ---
-//     zl.getGlobal("config");
-//     zl.tableGet(-1, "width");
-//     const width = zl.to(i64, -1);
-//     std.debug.print("width: {}\n", .{width});
-//     zl.pop(2);
-//
-//     // --- CTX ---
-//     const n = try zl.call(i64, "increment", .{});
-//     std.debug.print("counter: {}\n", .{n});
-//
-//     // --- LAST ERROR ---
-//     zl.exec(void, "nonexistent()") catch {};
-//     const err = zl.lastError();
-//     try std.testing.expect(err != null);
-//     std.debug.print("caught: {s}\n", .{err.?});
-// }
+    // --- ZLA ---
+    var zla: Self = try .init();
+    defer zla.deinit();
+
+    // --- APP ---
+    var app: App = .init(std.testing.allocator);
+    defer app.deinit();
+
+    // --- REGISTER METHODS & PUSH USERDATA ---
+    zla.registerMethods(App, &.{
+        .{ .name = "addUser", .func = App.addUser },
+    });
+    zla.pushUserdata(&app);
+    zla.setGlobal("app");
+
+    // --- EXEC FILE ---
+    try zla.execFromFile(
+        void,
+        "src/scripts/basic.lua",
+    );
+
+    // --- CALL ---
+    try zla.call(void, "addUser", .{ "abux", "25569" });
+    try zla.call(void, "addUser", .{ "jamal", "_stole123" });
+    try zla.call(void, "addUser", .{ "calico", "qwerty" });
+
+    // --- SHOW USERS ---
+    std.debug.print("\x1b[32m[USERS]\x1b[0m\n", .{});
+    for (app.users.items, 0..) |user, i| {
+        std.debug.print("\x1b[32m| [{}]\x1b[0m {s}: {s}\n", .{
+            i,
+            user.username,
+            user.password,
+        });
+    }
+}