C++ SDL Movement 播放器"duplication"？

我是 SDL 的初学者，我只是在 SDL 中尝试移动精灵。我在屏幕底部有一个矩形，您可以左右移动。但是，当您左右移动精灵时，它会"复制"，当您左右移动玩家时，会产生一种类似跟踪/贪吃蛇游戏的效果。关于如何解决这个问题的任何想法？

///the headers
#include "stdafx.h"
#include <SDL.h>
#include <SDL_image.h>
#include <string>
using namespace std;
//screen attributes
const int SCREEN_WIDTH = 800;
const int SCREEN_HEIGHT = 480;
const int SPRITE_SIZE = 32;
//the surfaces
SDL_Surface *image = NULL;
SDL_Surface *screen = NULL;
int main( int argc, char* argv[] )
{
SDL_Surface *screen, *temp,/* *temp2*/ *sprite/*, *sprite2*/;
SDL_Rect rcSprite/*, rcSprite2*/;
SDL_Event event;
Uint8 *keystate;
int gameover;
//initiailise sdl
SDL_Init(SDL_INIT_VIDEO);
SDL_WM_SetCaption("Pong Move Test", "Pong Move Test");
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 0, 0);
//load the sprite (paddle)
temp = SDL_LoadBMP("pongpaddle1.bmp");
sprite = SDL_DisplayFormat(temp);
SDL_FreeSurface(temp);

//set positions of sprite
rcSprite.x = 400;
rcSprite.y = 450;
gameover = 0;
//message pump
while (!gameover)
{
//look for an event
if (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
gameover = 1;
break;
case SDL_KEYDOWN:
switch (event.key.keysym.sym)
{
case SDLK_ESCAPE:
case SDLK_q:
gameover = 1;
break;
}
break;
}
}
//handle sprite movement
keystate = SDL_GetKeyState(NULL);
if (keystate[SDLK_LEFT])
{
rcSprite.x -= 1;
}
if (keystate[SDLK_RIGHT])
{
rcSprite.x += 1;
}
//colide with edges of screen
if (rcSprite.x < 0)
{
rcSprite.x =0;
}
else if (rcSprite.x > (SCREEN_WIDTH - SPRITE_SIZE))
{
rcSprite.x = (SCREEN_WIDTH - SPRITE_SIZE);
}

//draw the sprite
SDL_BlitSurface(sprite, NULL, screen, &rcSprite);
//update the screen
SDL_UpdateRect(screen, 0, 0, 0, 0);

}
//clean up area
SDL_FreeSurface(sprite);
SDL_Quit();

return 0;

}