# Is `self` a solved Rubix Cube ?
	fun is_solved: Bool do
		for face_id in [0 .. 6[ do
			var i = faces[face_id]
			var colour = i.first.first
			for j in [0 .. 3[ do
				var ln = i[j]
				for k in [0 .. 3[ do
					if ln[k] != colour then return false
				end
			end
		end
		return true
	end