Bare bones SNAKE game

This is the bare bones of a SNAKE game that I'm working on, the code runs as is, I've taken great care to keep my code clean and readable. I would appreciate feedback on my code. I plan on creating some graphics to greatly improve the presentation and a menu and high scores.

import sys
import random
import pygame

pygame.init()


class Snake:

    RED = (200, 0, 0)
    BLUE = (0, 0, 190)
    BLACK = (0, 0, 0)
    GREEN = (0, 230, 0)

    score = 0
    xpos = 80
    ypos = 16
    direction = (1, 0)
    snake_tail = [[16, 16], [32, 16], [48, 16], [64, 16], [80, 16]]

    keys = {"GO": pygame.KEYDOWN, "UP": pygame.K_UP, "DOWN": pygame.K_DOWN,
            "LEFT": pygame.K_LEFT, "RIGHT": pygame.K_RIGHT
            }

    fps = pygame.time.Clock()

    def __init__(self, width, height):

        self.width = width
        self.height = height
        self.food_x = random.randint(1, width - 1) * 16
        self.food_y = random.randint(1, height - 1) * 16
        self.screen = pygame.display.set_mode((width * 16, height * 16))

    def main_loop(self):

        while True:

            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    pygame.quit()
                    sys.exit()

                if event.type == self.keys["GO"] and event.key == self.keys["RIGHT"]:
                    self.direction = (1, 0)
                if event.type == self.keys["GO"] and event.key == self.keys["LEFT"]:
                    self.direction = (-1, 0)
                if event.type == self.keys["GO"] and event.key == self.keys["UP"]:
                    self.direction = (0, -1)
                if event.type == self.keys["GO"] and event.key == self.keys["DOWN"]:
                    self.direction = (0, 1)

            self.move_snake()
            self.fps.tick(12)

    def move_snake(self):

        self.xpos += self.direction[0] * 16
        self.ypos += self.direction[1] * 16
        self.snake_tail.append([self.xpos, self.ypos])
        segment = self.snake_tail.pop(0)

        pygame.draw.circle(self.screen, self.BLACK, (segment[0], segment[1]), 8)

        for segments in self.snake_tail:
            pygame.draw.circle(self.screen, self.BLUE, (segments[0], segments[1]), 8)

        pygame.draw.circle(self.screen, self.GREEN, (self.food_x, self.food_y), 8)
        pygame.draw.circle(self.screen, self.RED, (segments[0], segments[1]), 8)
        pygame.display.update()

        self.kill_snake()

    def kill_snake(self):

        if self.snake_tail[-1] in self.snake_tail[:-1]:
            pygame.quit()
            sys.exit()
        if self.xpos <= 0 or self.xpos >= self.width * 16 or self.ypos <= 0 or self.ypos >= self.height * 16:
            pygame.quit()
            sys.exit()

        self.feed_snake()

    def feed_snake(self):

        if self.xpos == self.food_x and self.ypos == self.food_y:
            self.score += 1
            pygame.display.set_caption(str(self.score))
            self.snake_tail.insert(0, [self.xpos, self.ypos])
            self.food_x = (random.randint(1, self.width - 1)) * 16
            self.food_y = (random.randint(1, self.height - 1)) * 16

Snake(25, 25).main_loop()