#include <conio.h>
#include <graphics.h>
#include<windows.h>
#define High 480  // 游戏画面尺寸
#define Width 640
// 全局变量
int ball_x, ball_y; // 小球的坐标
int ball_vx, ball_vy; // 小球的速度
int radius; // 小球的半径
int bar1_left, bar1_right, bar1_top, bar1_bottom; // 挡板1的上下左右位置坐标
int bar2_left, bar2_right, bar2_top, bar2_bottom; // 挡板2的上下左右位置坐标
int bar_height, bar_width; // 挡板的高度、宽度

void startup()  // 数据初始化
{
	ball_x = Width / 2;
	ball_y = High / 2;
	ball_vx = 1;
	ball_vy = 1;
	radius = 20;

	bar_width = Width / 30;
	bar_height = High / 2;

	bar1_left = Width * 1 / 20;
	bar1_top = High / 4;
	bar1_right = bar1_left + bar_width;
	bar1_bottom = bar1_top + bar_height;

	bar2_left = Width * 18.5 / 20;
	bar2_top = High / 4;
	bar2_right = bar2_left + bar_width;
	bar2_bottom = bar2_top + bar_height;

	initgraph(Width, High);
	BeginBatchDraw();
}

void clean()  // 消除画面
{
	setcolor(BLACK);
	setfillcolor(BLACK);
	fillcircle(ball_x, ball_y, radius);
	fillcircle(ball_x, ball_y, radius);
	bar(bar1_left, bar1_top, bar1_right, bar1_bottom);
	bar(bar2_left, bar2_top, bar2_right, bar2_bottom);
}

void show()  // 显示画面
{
	setcolor(GREEN);
	setfillcolor(GREEN);
	fillcircle(ball_x, ball_y, radius);	// 绘制绿圆	

	setcolor(YELLOW);
	setfillcolor(YELLOW);
	bar(bar1_left, bar1_top, bar1_right, bar1_bottom);	// 绘制黄色挡板
	bar(bar2_left, bar2_top, bar2_right, bar2_bottom);

	FlushBatchDraw();
	// 延时
	Sleep(1);
}

void updateWithoutInput()  // 与用户输入无关的更新
{
	// 挡板和小圆碰撞，小圆反弹
	if (ball_x + radius >= bar2_left && ball_y + radius >= bar2_top && ball_y + radius <= bar2_bottom)
		ball_vx = -ball_vx;
	else if (ball_x - radius <= bar1_right && ball_y + radius >= bar1_top && ball_y + radius <= bar1_bottom)
		ball_vx = -ball_vx;

	// 更新小圆坐标
	ball_x = ball_x + ball_vx;
	ball_y = ball_y + ball_vy;

	if ((ball_x <= radius) || (ball_x >= Width - radius))
		ball_vx = -ball_vx;
	if ((ball_y <= radius) || (ball_y >= High - radius))
		ball_vy = -ball_vy;
}

void updateWithInput()  // 与用户输入有关的更新
{
	int step = 1;
	if (GetAsyncKeyState(0x57) & 0x8000)  // w
		bar1_top -= step;
	if ((GetAsyncKeyState(0x53) & 0x8000)) //s
		bar1_top += step;
	if ((GetAsyncKeyState(VK_UP) & 0x8000))     // 上方向键
		bar2_top -= step;
	if ((GetAsyncKeyState(VK_DOWN) & 0x8000))  // 下方向键
		bar2_top += step;

	bar1_bottom = bar1_top + bar_height;
	bar2_bottom = bar2_top + bar_height;
}

void gameover()
{
	EndBatchDraw();
	closegraph();
}

int main()
{
	startup();  // 数据初始化	
	while (1)  //  游戏循环执行
	{
		clean();  // 把之前绘制的内容取消
		updateWithoutInput();  // 与用户输入无关的更新
		updateWithInput();     // 与用户输入有关的更新
		show();  // 显示新画面
	}
	gameover();     // 游戏结束、后续处理
	return 0;
}