#include <graphics.h>
#include <stdlib.h>
#include <dos.h>
/*定義控制命令*/
#define LEFT  0x4b00
#define RIGHT 0x4d00
#define DOWN  0x5000
#define UP 	  0x4800
#define ESC   0x011b

/*定義蛇的最大節數*/
#define NODE 200

int i,key;
int score=0;/*得分*/
/*定義游戲速度*/
int SPEED=100;
/*定義食物的結構體*/
struct Food
{
   int x;/*食物的橫坐標*/
   int y;/*食物的縱坐標*/
   int need;/*判斷是否要出現食物的變量*/
};
/*定義蛇的結構體*/
struct Snake
{
   int x[NODE];
   int y[NODE];
   int node;/*蛇的節數*/
   int direction;/*蛇移動方向*/
   int life;/* 蛇的生命,0活著,1死亡*/
};

struct Food food;
struct Snake snake;
/*開始畫面，左上角坐標為（50，40），右下角坐標為（600，450）的圍墻*/
void DrawFence(void)
{
   setcolor(WHITE);
   /*畫圍墻的上邊*/
   line(50,40,600,40);
   line(50,42,600,42);
   /*畫圍墻的下邊*/
   line(50,450,600,450);
   line(50,452,600,452);
	 /*畫圍墻的左邊*/
	 line(50,40,50,450);
	 line(52,40,52,450);
	 /*畫圍墻的右邊*/
	 line(600,40,600,450);
	 line(602,40,602,450);
}

/*輸出成績*/
void PrintScore()
{   
   char string[10];
   setfillstyle(SOLID_FILL,YELLOW);
   bar(50,15,220,35);
   setcolor(RED);
   settextstyle(0,0,2);
   sprintf(string,"score:%d",score);
   outtextxy(55,20,string);
}
/*游戲結束*/
void GameOver()
{
   cleardevice(); 
   PrintScore();
   setcolor(RED);
   settextstyle(0,0,4);
   outtextxy(200,200,"GAME OVER");
   getch();
}
/*畫蛇函數*/
void DrawSnake()
{
	setcolor(4);
	for(i=0;i<snake.node;i++)
		rectangle(snake.x[i],snake.y[i],snake.x[i]+10,snake.y[i]-10);
  delay(SPEED);
  setcolor(0);
  rectangle(snake.x[snake.node-1],snake.y[snake.node-1],
	snake.x[snake.node-1]+10,snake.y[snake.node-1]-10);
}
/*玩游戲具體過程*/
void PlayGame()
{
   randomize();/*隨機數發生器*/
   food.need=1;/*1表示需要出現新食物,0表示已	經存在食物*/
   snake.life=0;/*活著*/
   /*方向往右*/
   snake.direction=1;
   /*蛇頭*/
   snake.x[0]=100;
   snake.y[0]=100;
   snake.x[1]=110;
   snake.y[1]=100;
   snake.node=2;/*節數*/
   PrintScore();/*輸出得分*/
   while(1)/*可以重復玩游戲,壓ESC鍵結束*/
   {
      while(!kbhit())/*在沒有按鍵的情況下,蛇自己移動身體*/
      {
	 			if(food.need==1)/*需要出現新食物*/
	 			{
	   			food.x=rand()%400+60;
	   			food.y=rand()%350+60;
	   			while(food.x%10!=0)/*食物隨機出現后必須讓食物能夠在整格內,這樣才可以讓蛇吃到*/
						food.x++;
	   			while(food.y%10!=0)
						food.y++;
		 			food.need=0;/*畫面上有食物了*/
	 			}
	 			if(food.need==0)/*畫面上有食物了就要顯示*/
	 			{
      		setcolor(GREEN);
      		rectangle(food.x,food.y,food.x+10,food.y-10);
	 			}
        for(i=snake.node-1;i>0;i--)/*蛇的每個環節往前移動,也就是貪吃蛇的關鍵算法*/
        {
          snake.x[i]=snake.x[i-1];
	    		snake.y[i]=snake.y[i-1];
	 			}
       /*1,2,3,4表示右,左,上,下四個方向,通過這個判斷來移動蛇頭*/
	 			switch(snake.direction)
	 			{
	    		case 1:snake.x[0]+=10;break;
	    		case 2: snake.x[0]-=10;break;
	    		case 3: snake.y[0]-=10;break;
	   			case 4: snake.y[0]+=10;break;
	 			}
	 			for(i=3;i<snake.node;i++)/*從蛇的第四節開始判斷是否撞到自己了，因為蛇頭為兩節，第三節不可能拐過來*/
	 			{
	    		if(snake.x[i]==snake.x[0]&&snake.y[i]==snake.y[0])
	    		{
            GameOver();/*顯示失敗*/
            snake.life=1;
            break;
	    		}
        }
				if(snake.x[0]<55||snake.x[0]>595||snake.y[0]<55||snake.y[0]>455)/*蛇是否撞到墻壁*/
				{
	    		GameOver();/*本次游戲結束*/
	    		snake.life=1; /*蛇死*/
				}
				if(snake.life==1)/*以上兩種判斷以后,如果蛇死就跳出內循環，重新開始*/
           break;
				if(snake.x[0]==food.x&&snake.y[0]==food.y)/*吃到食物以后*/
				{
          setcolor(0);/*把畫面上的食物東西去掉*/
          rectangle(food.x,food.y,food.x+10,food.y-10);
	   			snake.x[snake.node]=-20;snake.y[snake.node]=-20;
          /*新的一節先放在看不見的位置,下次循環就取前一節的位置*/
	   			snake.node++;/*蛇的身體長一節*/
	   			food.need=1;/*畫面上需要出現新的食物*/
	   			score+=10;
	  		  PrintScore();/*輸出新得分*/
				}
				DrawSnake();
     	}
    	if(snake.life==1)/*如果蛇死就跳出循環*/
        break;
      key=bioskey(0);/*接收按鍵*/
    	if(key==ESC)/*按ESC鍵退出*/
        break;
    	else if(key==UP&&snake.direction!=4)
				/*判斷是否往相反的方向移動*/
	  		snake.direction=3;
      else if(key==RIGHT&&snake.direction!=2)
	     	snake.direction=1;
	  	else if(key==LEFT&&snake.direction!=1)
				snake.direction=2;
	    else if(key==DOWN&&snake.direction!=3)
		   	snake.direction=4;
   }
}
/*主函數*/
void main(void)
{
   int gd=DETECT,gm;
   initgraph(&gd,&gm,"e:\\tc");
   cleardevice();
   /*繪制邊框*/
   DrawFence();
   /*玩游戲具體過程*/
   PlayGame();
   getch();
   closegraph();
}