Add combat combo gameplay

scenes/combat/combo_window.gd

@@ -0,0 +1,55 @@
+class_name ComboWindow
+extends RefCounted
+
+signal window_cleared(reason: String)
+
+const SIZE := 4
+
+var slots: Array[String] = []
+var pending_clear_reason := ""
+
+
+func record(input: String) -> void:
+	if input.is_empty():
+		return
+	slots.append(input)
+	if slots.size() >= SIZE:
+		pending_clear_reason = "full"
+
+
+func get_slots() -> Array[String]:
+	return slots.duplicate()
+
+
+func has_pending_clear() -> bool:
+	return not pending_clear_reason.is_empty()
+
+
+func consume_pending_clear_reason() -> String:
+	var reason := pending_clear_reason
+	pending_clear_reason = ""
+	return reason
+
+
+func get_pattern() -> String:
+	var pattern := ""
+	for slot: String in slots:
+		if slot != "Ø":
+			pattern += slot
+	return pattern
+
+
+func get_contiguous_pattern() -> String:
+	var pattern := ""
+	for index: int in range(slots.size() - 1, -1, -1):
+		var slot := slots[index]
+		if slot == "Ø":
+			break
+		pattern = slot + pattern
+	return pattern
+
+
+func clear(reason := "") -> void:
+	slots.clear()
+	pending_clear_reason = ""
+	window_cleared.emit(reason)