Snake Game-贪吃蛇

原文网址:http://www.simonhuggins.com/courses/cbasics/course_notes/snake.htm

 

Introduction

The following is an example game written in C based on the game called 'snake' which has been around since the earliest days of home computing (I can remember writing a version of it for my ZX81), and has re-emerged in recent years on mobile phones.

It isn't the world's greatest game, but it does give you an idea of what you can achieve with a relatively simple C program, and perhaps the basis by which to extend the principles and create more interesting games of your own.

Playing the game

You can download the executable to try out the game without having to compile it if you wish. Download it by clicking here - it is about 123k in length.

Note that on faster PCs, it will be unplayably fast, so you will need to re-compile it  with the pause_length constant set to a higher value. My PC is about 350MHz and it is OK.

To move the snake, use 'a' for up, 'z' for down, 'o' for left and 'p' for right. Again, there are constants you can change if you want to alter these settings. Press 'x' to exit the game at any time.

The aim of the game is to collect the dots (food) and avoid the obstacles (crosses, borders, and the snake itself). As you collect food, the snake gets longer, so increasing your likelihood of crashing into yourself. When you have collected enough food, you progress onto the next level, where your snake gets longer, and the amount of food to collect to progress through the level gets larger.

You get scored according to the length of the snake and the number of 'x' obstacles on the screen.

The speed increases every 5 levels.

You get a bonus when you complete the level of 1000, increasing by 1000 each level (e.g. complete level 5, you get a 5000 bonus).

There is no concept of lives. Once you hit an obstacle, that's it, game over.

Make sure you do not have the caps lock on, otherwise the keys will fail to respond.

The Listing

This is the C program for the game. it is reasonably well structured, but by no means perfect.  Note that it uses library functions that are not available on all C compilers - it was designed using Borland C++ Builder / Turbo C.  Also it uses a few C++ concepts not available in standard C - e.g. const for a constant (you would use #define in normal C). You may also have to change your compiler settings if you have them set to ANSI C to C++ instead - the for loops define a local instance of i as a loop counter, a concept to available in standard C.

#include <stdlib.h>#include <stdio.h>#include <conio.h>/* prototypes */void draw_line(int col, int row);void show_score();void add_segment();void setup_level();/* constants */const int maxrow=15, maxcol=77;const int snake_start_col=33,snake_start_row=7;const char up_key='a', down_key='z', left_key='o', right_key='p';const int pause_length=500000;/* global variables */int score, snake_length, speed, obstacles, level, firstpress, high_score=0;char screen_grid[maxrow][maxcol];char direction = right_key;struct snake_segment { int row,col;} snake[100];void main(){ /* Variable declarations within main() only */ char keypress; do /* restart game loop */ { obstacles=4; level=1; score=0; speed=14; randomize(); /* Ensure random seed initiated */ setup_level(); /* main loop */ do { for (int i=0;i<(speed*pause_length);i++) int j=1+i; /*pause*/ /* If key has been hit, then check it is a direction key - if so, change direction */ if (kbhit()) { keypress=(char)getch(); if((keypress==right_key)||(keypress==left_key)|| (keypress==up_key)||(keypress==down_key)) direction = keypress; } /* Add a segment to the end of the snake */ add_segment(); /* Blank last segment of snake */ gotoxy(snake[0].col,snake[0].row); cprintf(" "); /* ... and remove it from the array */ for (int i=1;i<=snake_length;i++) snake[i-1]=snake[i]; /* Display snake in yellow */ textcolor(YELLOW); for (int i=0;i<=snake_length;i++) { gotoxy(snake[i].col,snake[i].row); cprintf("O"); } /* keeps cursor flashing in one place instead of following snake */ gotoxy(1,1); /* If first press on each level, pause until a key is pressed */ if (firstpress) { while(!kbhit()); firstpress = 0; } /* Collision detection - walls (bad!) */ if ((snake[snake_length-1].row>maxrow+1)||(snake[snake_length-1].row<=1)|| (snake[snake_length-1].col>maxcol+1)||(snake[snake_length-1].col<=1)|| /* Collision detection - obstacles (bad!) */ (screen_grid[snake[snake_length-1].row-2][snake[snake_length-1].col-2]=='x')) keypress='x'; /* i.e. exit loop - game over */ /* Collision detection - snake (bad!) */ for (int i=0;i<snake_length-1;i++) if ( (snake[snake_length-1].row)==(snake[i].row) && (snake[snake_length-1].col)==(snake[i].col)) { keypress='x'; /* i.e. exit loop - game over */ break; /* no need to check any more segments */ } /* Collision detection - food (good!) */ if (screen_grid[snake[snake_length-1].row-2][snake[snake_length-1].col-2]=='.') { /* increase score and length of snake */ score+=snake_length*obstacles; show_score(); snake_length++; add_segment(); /* if length of snake reaches certain size, onto next level */ if (snake_length==(level+3)*2) { score+=level*1000; obstacles+=2; level++; /* add to obstacles */ if ((level%5==0)&&(speed>1)) speed--; /* increase speed every 5 levels */ setup_level(); /* display next level */ } } } while (keypress!='x'); /* game over message */ if (score > high_score) high_score = score; show_score(); gotoxy(30,6); textcolor(LIGHTRED); cprintf("G A M E O V E R"); gotoxy(30,9); textcolor(YELLOW); cprintf("Another Game (y/n)? "); do keypress=getch(); while((keypress!='y')&&(keypress!='n')); } while (keypress=='y');}void setup_level(){ /* variables local to setup_level() */ int row,col; /* Set up global variables for new level */ snake_length=level+4; direction = right_key; firstpress = 1; /* Fill grid with blanks */ for(row=0;row<maxrow;row++) for(col=0;col<maxcol;col++) screen_grid[row][col]= ' '; /* Fill grid with Xs and food */ for(int i=0;i<obstacles*2;i++) { row= rand()%maxrow; col= rand()%maxcol; if(i<obstacles) screen_grid[row][col]='x'; else screen_grid[row][col]='.'; } /* Create snake array of length snake_length */ for(int i=0;i<snake_length;i++) { snake[i].row=snake_start_row; snake[i].col=snake_start_col+i; } /* Draw playing board */ draw_line(1,1); for(row=0;row<maxrow;row++) { gotoxy(1,row+2); textcolor(LIGHTBLUE); cprintf("|"); textcolor(WHITE); for(col=0;col<maxcol;col++) cprintf("%c",screen_grid[row][col]); textcolor(LIGHTBLUE); cprintf("|"); } draw_line(1,maxrow+2); show_score(); gotoxy(2,maxrow+5); textcolor(LIGHTRED); cprintf("~~ SNAKE GAME~~ Left: %c, Right: %c, Up: %c, Down: %c, Exit: x. Any key to start.", left_key,right_key,up_key,down_key);}void draw_line(int col, int row){ gotoxy(col,row); textcolor(LIGHTBLUE); for (int col=0;col<maxcol+2;col++) cprintf("=");}void show_score(){ textcolor(LIGHTCYAN); gotoxy(2,maxrow+3); cprintf("Level: %05d",level); gotoxy(40,maxrow+3); textcolor(LIGHTGREEN); cprintf("Score: %05d",score); gotoxy(60,maxrow+3); textcolor(LIGHTMAGENTA); cprintf("High Score: %05d",high_score);}void add_segment(){ switch(direction) { case(right_key): snake[snake_length].row=snake[snake_length-1].row; snake[snake_length].col=snake[snake_length-1].col+1; break; case(left_key) : snake[snake_length].row=snake[snake_length-1].row; snake[snake_length].col=snake[snake_length-1].col-1; break; case(up_key) : snake[snake_length].row=snake[snake_length-1].row-1; snake[snake_length].col=snake[snake_length-1].col; break; case(down_key) : snake[snake_length].row=snake[snake_length-1].row+1; snake[snake_length].col=snake[snake_length-1].col; }}