Python Pygame Simple Menu

import sys
import pygame

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (128, 0, 0)
GREEN = (0, 128, 0)
BLUE = (0, 0, 128)

pygame.init()
PDR = pygame.Rect(0, 0, 1024, 720)
PDS = pygame.display.set_mode(PDR.size)
FPS = 120

pygame.font.init()
FONT = pygame.font.SysFont('Ariel', 35)

class menu:
    class item:
        def __init__(s, text, identifier = None):
            global FONT, WHITE, BLACK, RED

            s.id = identifier
            s.text = text
            if id:
                s.highlighted_surface = FONT.render(text, True, WHITE, RED)
            s.unhighlighted_surface = FONT.render(text, True, WHITE, BLACK)
            s.rect = s.unhighlighted_surface.get_rect()

    def __init__(s):
        s.itemContainer = []
        s.highlightableContainer = []

        s.selected = None

        s.menuHeight = 0
        test = s.item("TEST")
        s.itemHeight = test.rect.h
        del test

        s.keyDown = False

    def addItem(s, text, identifier = None):
        newItem = s.item(text, identifier)

        s.itemContainer.append(newItem)

        if identifier:
            s.highlightableContainer.append(newItem)

        s.menuHeight += s.itemHeight

    def draw(s):
        global PDS, PDR

        y = (PDR.h - s.menuHeight) / 2

        for item in s.itemContainer:
            x = (PDR.w - item.rect.w) / 2

            if item == s.highlightableContainer[0]:
                PDS.blit(item.highlighted_surface, (x, y))
            else:
                PDS.blit(item.unhighlighted_surface, (x, y))

            y += s.itemHeight

    def update(s):
        if not s.highlightableContainer: return

        k = pygame.key.get_pressed()
        if k[pygame.K_UP] and not s.keyDown:
            s.highlightableContainer = [s.highlightableContainer[-1]] + s.highlightableContainer[:-1]
            s.keyDown = True
        elif k[pygame.K_DOWN] and not s.keyDown:
            s.highlightableContainer = s.highlightableContainer[1:] + [s.highlightableContainer[0]]
            s.keyDown = True
        elif not k[pygame.K_UP] and not k[pygame.K_DOWN] and s.keyDown:
            s.keyDown = False

        if k[pygame.K_SPACE] or k[pygame.K_RETURN]:
            s.selected = s.highlightableContainer[0]


m = menu()
m.addItem("M E N U")
m.addItem(" ")
m.addItem("LET'S DO THIS", "PLAY")
m.addItem("WIMP OUT!", "EXIT")
m.addItem(" ")
m.addItem("OPTIONS", "OPTIONS")

while True:
    events = pygame.event.get()
    for e in events:
        if e.type == pygame.QUIT: sys.exit()

    PDS.fill(BLACK)
    m.draw()
    m.update()
    if m.selected:
        if m.selected.id == "EXIT": break

    pygame.display.update()
    pygame.time.Clock().tick(FPS)

pygame.quit()
sys.exit()