feat: Implement core multiplayer features including user authentication, profile management, lobby, game mode managers, and leaderboard.

scripts/ui/login_screen.gd

@@ -22,10 +22,14 @@ extends Control
 @onready var reg_confirm_password_input := %RegConfirmPasswordInput as LineEdit
 @onready var password_strength := %PasswordStrength as ProgressBar
 @onready var password_hint := %PasswordHint as Label
+@onready var reg_captcha_question := %RegCaptchaQuestion as Label
+@onready var reg_captcha_input := %RegCaptchaInput as LineEdit
 @onready var register_button := %RegisterButton as Button
 @onready var back_to_login_link := %BackToLoginLink as LinkButton
 @onready var reg_status_label := %RegStatusLabel as Label
 
+var current_captcha_answer: int = 0
+
 # Main panel reference
 @onready var main_panel := $CenterContainer/MainPanel as PanelContainer
 
@@ -101,8 +105,16 @@ func _show_registration() -> void:
 	main_panel.visible = false
 	registration_panel.visible = true
 	reg_status_label.text = ""
+	_generate_captcha()
 	reg_email_input.grab_focus()
 
+func _generate_captcha() -> void:
+	var num1 := randi_range(1, 10)
+	var num2 := randi_range(1, 10)
+	current_captcha_answer = num1 + num2
+	reg_captcha_question.text = "Security Check: %d + %d = ?" % [num1, num2]
+	reg_captcha_input.text = ""
+
 func _show_login() -> void:
 	registration_panel.visible = false
 	main_panel.visible = true
@@ -254,6 +266,7 @@ func _on_register_pressed() -> void:
 	var username := reg_username_input.text.strip_edges()
 	var password := reg_password_input.text
 	var confirm_password := reg_confirm_password_input.text
+	var captcha_answer := reg_captcha_input.text.strip_edges()
 	
 	# Validation
 	if email.is_empty():
@@ -288,6 +301,15 @@ func _on_register_pressed() -> void:
 		_show_reg_error("Password is too weak. Add numbers or symbols.")
 		return
 	
+	if captcha_answer.is_empty():
+		_show_reg_error("Please solve the security check.")
+		return
+		
+	if not captcha_answer.is_valid_int() or int(captcha_answer) != current_captcha_answer:
+		_show_reg_error("Incorrect security check answer.")
+		_generate_captcha()
+		return
+	
 	AuthManager.register_with_email(email, password, username)
 
 func _check_password_strength(password: String) -> void:
@@ -411,6 +433,7 @@ func _set_inputs_enabled(enabled: bool) -> void:
 	reg_username_input.editable = enabled
 	reg_password_input.editable = enabled
 	reg_confirm_password_input.editable = enabled
+	reg_captcha_input.editable = enabled
 
 func _is_valid_email(email: String) -> bool:
 	# Simple email validation