#include<stdio.h>
#include<windows.h>
#include<graphics.h>

#define WIDTH 960
#define HEIGTH 640
#define STR_SIZE 20
#define STR_NUM 128
#define STR_WIDTH 15

struct Rain {
	int x;
	int y;
	int speed;
	char str[STR_SIZE];
} rain[STR_NUM];

char CreateChar() {
	char temp = 0;
	int flag = rand() % 3;
	if(flag == 0) {
		temp = rand() % 26 + 'a';
//		temp = 'a';
	} else if(flag == 1) {
		temp = rand() % 26 + 'A';
//		temp ='A';
	} else {
		temp = rand() % 10+'0';
//		temp = '0';
	}
	
	return temp;
}

void GameInit(){
	for (int i= 0; i < STR_NUM; i++) {
		rain[i].x = i * STR_WIDTH;
		rain[i].y = rand() % HEIGTH;
		rain[i].speed = rand() % 5 + 5;
	}
	for (int i = 0; i < STR_NUM; i++) {
		for (int j = 0; j < STR_SIZE; j++) {
			rain[i].str[j] = CreateChar();
		}
		
	}
}

void GameDraw(){
	cleardevice();
	for (int i = 0; i < STR_NUM; i++) {
		for (int j = 0; j < STR_SIZE; j++) {
			outtextxy(rain[i].x, rain[i].y - STR_WIDTH * j, rain[i].str[j]);
			SetTextColor(RGB(0, 255 - 13 * j, 0));
		}
	}
}
void GamePlay(){
	for (int i = 0; i < STR_NUM; i++) {
		rain[i].y += rain[i].speed;
		if (rain[i].y - STR_SIZE * STR_WIDTH > HEIGTH) {
			rain[i] = 0;
		}
	}
}
void ChangeCh(){
	for(int i=0;i<STR_NUM;i++){
		rain[rand()%STR_NUM].str[rand()%STR_SIZE]=CraeteChar();
	}
}
int main(){
	initgraph(WIDTH,HEIGTH);
	srand(GetTickCount());
	GameInit();
	DWORD t1, t2;
	t1 = t2 = GetTickCount();
	while (1) {
		BeginBatchDraw();
		GameDraw();
		ChangeCh();
		if (t2 - t1 > 20){
			GamePlay();
			t1 = t2;
		}
		t2 = GetTickCount();
		EndBatchDraw();
		// Sleep(20);
	}
	
	getchar();
	closegraph();
	return 0;
	
}