复制代码
代码如下：
<！-要更改此模板，请选择“工具”|“模板，然后在编辑器中打开模板。-><！DOCTYPEhtml><html><head><title>乒乓球游戏</title><metahttp-equiv=“Content-Type”content=“text/html;charset=utf-8”><脚本>varctx;varcanvas;varball_x=10;varball_y=10;varball_radius=10;varball_vx=10;varball_vy=8;varwall_x=30;varwall_y=40;varwall_width=30;varwall_height=60;varbox_x=0;varbox_y=0;varbox_width=300;varbox_height=300;varbound_left=box_x+ball_radius;
varbound_right=box_x+box_width-ball_radius;varbound_top=box_y+ball_radius;varbound_bottom=box_y+box_height-ball_radius;varunit=10;函数intersect（sx，sy，fx，fy，cx，cy，rad）{vardx;vardy;vart;varrt;dx=fx-sx;dy=fy-sy;t=0.0-（（（（sx-cx）*dx+（sy-cy）*dy）/（dx*dx+dy*dy）））;如果（t<0.0）{t=0.0;}if（t>1.0）t=1.0;vardx1=（sx+t*dx）-cx;vardy1=（sy+t*dy）-cy;varrt=dx1*dx1+dy1*dy1;如果（rt<rad*rad）返回true;否则返回假；
}函数move_ball（）{ball_x=ball_x+ball_vx;ball_y=ball_y+ball_vy;if（ball_x<bound_left）{ball_x=bound_left;ball_vx=-ball_vx;}if（ball_x>bound_right）{ball_x=bound_right;ball_vx=-ball_vx;}if（ball_y<bound_top）{ball_y=bound_top;ball_vy=-ball_vy;}if（ball_y>bound_bottom）{ball_y=bound_bottom;ball_vy=-ball_vy;}//撞到上边if（intersect（wall_x，wall_y，wall_x+wall_width，wall_y+wall_height，ball_x，ball_y，ball_radius））{ball_y=wall_y-ball_radius;
ball_vy=-ball_vy;}//撞到左边if（intersect（wall_x，wall_y，wall_x，wall_y+wall_height，ball_x，ball_y，ball_radius））{ball_x=wall_x-ball_radius;ball_vx=-ball_vx;}//撞到右边if（intersect（wall_x+wall_width，wall_y，wall_x+wall_width，wall_y+wall_height，ball_x，ball_y，ball_radius））{ball_x=wall_x+wall_width+ball_radius;ball_vx=-ball_vx;}//撞到下边if（intersect（wall_x，wall_y+wall_height，wall_x+wall_width，wall_y+wall_height，ball_x，ball_y，ball_radius））{ball_y=wall_y+wall_height+ball_radius;ball_vy=-ball_vy;}}函数move_wall（ev）{varkeyCode;
if（event==null）{keyCode=window.event.keyCode;window.event.preventDefault（）;}else{keyCode=event.keyCode;event.preventDefault（）;}switch（keyCode）{case37：//left;wall_x-=unit;if（wall_x<bound_left）wall_x=bound_left;打破;案例38：//upwall_y-=unit;if（wall_y<bound_top）wall_y=bound_top;打破;案例39：//rightwall_x+=unit;if（wall_x+wall_width>bound_right）wall_x=bound_right-wall_width;打破;案例40：//downwall_y+=unit;
if（wall_y+wall_height>bound_bottom）wall_y=bound_bottom-wall_height;打破;默认值：break;}}函数draw_all（）{ctx.beginPath（）;ctx.clearRect（box_x，box_y，box_width，box_height）;ctx.fillStyle=“rgb（255,0,0）”;//ctx.lineWidth=ball_radius;ctx.arc（ball_x，ball_y，ball_radius，0，Math.PI*2，true）;ctx.fill（）;//注意ctx.fillStyle=“rgb（0,0,0）”;ctx.fillRect（wall_x，wall_y，wall_width，wall_height）;ctx.strokeRect（box_x，box_y，box_width，box_height）;}函数init（）{canvas=document.getElementById（'canvas'）;ctx=canvas.getContext（'2d'）;draw_all（）;
setInterval（draw_all，100）;setInterval（move_ball，50）;window.addEventListener（'keydown'，move_wall，false）;//注释}</script></head><bodyonLoad=“init（）;”><canvasid=“canvas”width=“300”height=“300”></canvas></body></html>
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