add game state

game/src/GameState.gd

@@ -0,0 +1,25 @@
+extends Node
+class_name GameState
+
+# https://github.com/GDQuest/godot-demos/blob/master/2018/04-24-finite-state-machine/player_v2/state_machine.gd
+# http://www.gameprogrammingpatterns.com/state.html
+
+enum State { MAIN, WINNING, GAME_OVER }
+var transitions = {
+	State.MAIN : [ State.WINNING ],
+	State.WINNING : [ State.GAME_OVER ],
+	State.GAME_OVER : [ State.MAIN ]
+}
+
+signal state_changed(previous, current)
+
+export(State) var current_state = State.MAIN
+
+func current_state_name() -> String:
+	return State.keys()[current_state]
+
+func transition_to(state):
+	assert(state in transitions[current_state])
+	var previous_state = current_state
+	current_state = state
+	emit_signal("state_changed", previous_state, current_state)