Simple Pygame Sprite Button

import pygame
from pygame.sprite import Sprite

class Button(Sprite):
    def __init__(self, caption, font, rect, callback,
            text_color=pygame.Color('white'),
            button_color=pygame.Color('slateblue'),
            hover_color=pygame.Color('dodgerblue')):

        Sprite.__init__(self)
        self.rect = rect
        self.hover = False
        self.callback = callback

        # Build are text and center it
        image_caption = font.render(caption, 1, text_color)
        image_rect = image_caption.get_rect()
        image_rect.center = pygame.Vector2(rect.center) - rect.topleft

        # Build are normal image
        self.image_normal = pygame.Surface(rect.size)
        self.image_normal.fill(button_color)
        self.image_normal.blit(image_caption, image_rect)

        # Build are hover image
        self.image_hover =  pygame.Surface(rect.size)
        self.image_hover.fill(hover_color)
        self.image_hover.blit(image_caption, image_rect)

    # Override image to control the draw method
    @property
    def image(self):
        if self.hover:
            return self.image_hover
        else:
            return self.image_normal

    def on_mousemotion(self, event):
        self.hover = self.rect.collidepoint(event.pos)

    def on_clicked(self, event):
        if event.button == 1:
            if self.rect.collidepoint(event.pos):
                self.callback(self)