Move "computer" related state to the OldComputer singleton.

old_computer.gd

@@ -1,7 +1,34 @@
 extends CanvasLayer
 
+var disks_wanted = [1, 2, 3, 4]
+var disks_loaded = []
+
+var starting_integrity = 2
+var total_integrity = starting_integrity + len(disks_wanted)
+
 func _ready() -> void:
-	$ConsoleText.text = $ConsoleText.text % %Pharaoh.get_memory_integrity()
+	$ConsoleText.text = $ConsoleText.text % get_memory_integrity()
+
+func load_disk(disk_num: int) -> bool:
+	if !disk_num or (disk_num in disks_loaded):
+		return false
+	
+	disks_loaded.push_back(disk_num)
+	disks_wanted.remove_at(disks_wanted.find(disk_num))
+	
+	print("Loaded up disk ", disk_num)
+	printline(
+		">> Loaded data disk %d (of %d). Memory integrity now at %d%%" % 
+		[disk_num, len(disks_wanted) + len(disks_loaded), get_memory_integrity()]
+	)
+
+	return true
+
+func get_next_disk_num() -> int:
+	return disks_wanted.front()
+
+func get_memory_integrity():
+	return 100.0 / total_integrity * (starting_integrity + len(disks_loaded))
 
 func open() -> void:
 	visible = true