Add objectives listing and all four data disks/tablets.

Track each individual disk and ensure they are loaded in order.
Player can collect multiple disks in one run but must present them
to the pharaoh in order.

player_2d.gd

@@ -19,6 +19,7 @@ var death_threshold = 1000
 var coins = 0
 
 var data_disks = []
+var objectives = {}
 
 func _ready() -> void:
 	DisplayServer.window_set_title("JUMPS EQUALS JUMPS")
@@ -43,12 +44,25 @@ func refresh_jump(new_jumps):
 func give_disk(disk_num: int) -> void:
 	data_disks.push_back(disk_num)
 
-func take_disk() -> int:
-	var disk_num = data_disks.pop_back()
-	if disk_num:
-		return disk_num
-	return 0
-	
+func take_disk(disk_num) -> bool:
+	if not has_disk(disk_num):
+		return false
+
+	data_disks.remove_at(data_disks.find(disk_num))
+	return true
+
+func has_disk(disk_num: int) ->  bool:
+	return disk_num in data_disks
+
+func give_objective(id: String, description: String) -> void:
+	objectives[id] = description
+
+func has_objective(id: String) ->  bool:
+	return objectives.has(id)
+
+func complete_objective(id: String) -> bool:
+	return objectives.erase(id)
+
 func on_teleport():
 	refresh_jump(1)
 	teleport_cooldown = 1