#include <easyx.h>
#include <conio.h>
#include <list>
using namespace std;

int sx = 25;
int sy = 25;
int x;
int y;
char ch = 'd';
char score[12];
int m = (rand()%64)*10+5;
int n = (rand()%46)*10+35;
int length=3;
list<char> lc;
list<char>::iterator lci;

int main()
{
    initgraph(640,480);

    outtextxy(180, 200, "set of key: 'w':up 's':down 'a':left 'd':right");
    outtextxy(200, 230, "press any key to start the game");
    settextstyle(30,20,_T("微软雅黑"));
    outtextxy(150,150,"Greedy Snake 1.0");
    getch();

    settextstyle(20,10,_T("΢ÈíÑźÚ"));
    lc.push_back(ch);
    lc.push_back(ch);
    while(true)
    {
        //draw the snake
        fillcircle(sx,sy,5);
        x=sx;
        y=sy;
        for(int i=0; i<length-1 ;++i)
        {
            if(i==0)
                lci=--lc.end(); 
            else
                --lci;
            switch(*lci)
            {
            case 'w':
                fillcircle(x,y+=10,5);
                break;
            case 'a':
                fillcircle(x+=10,y,5);
                break;
            case 's':
                fillcircle(x,y-=10,5);
                break;
            case 'd':
                fillcircle(x-=10,y,5);
                break;
            }
        }
        //draw random circle
        fillcircle(m,n,5);
        //detect keybord input
        if(kbhit())
            ch=getch();
        switch(ch)
        {
        case 'w':
            if(lc.back()!='s')
                sy-=10;
            else
            {
                ch='s';
                sy+=10;
            }
            break;
        case 'a':
            if(lc.back()!='d')
                sx-=10;
            else
            {
                ch='d';
                sx+=10;
            }
            break;
        case 's':
            if(lc.back()!='w')
                sy+=10;
            else
            {
                ch='w';
                sy-=10;
            }
            break;
        case 'd':
            if(lc.back()!='a')
                sx+=10;
            else
            {
                ch='a';
                sx-=10;
            }
            break;
        default:
            getch();
            ch=lc.back();
            break;
        }
        //put direction into the list
        lc.push_back(ch);
        //dectect collision
        if(sy<25 || sx<0 || sy>475 || sx>635)
        {
            settextstyle(50,30,_T("微软雅黑"));
            outtextxy(130,200,"GAME OVER");
            break;
        }
        //detect eat or not
        if(sx==m&&sy==n)
        {
            length+=1;
            m = (rand()%64)*10+5;
            n = (rand()%47)*10+15;
            fillcircle(m,n,5);
        }
        else
            lc.pop_front();
        //display the picture
        Sleep(100);
        cleardevice();
        //draw the score
        sprintf(score,"score: %04d",length-3);
        outtextxy(270,0,score);
        line(0,20,640,20);
    }

    getch();
    closegraph();
    return 0;
}