* {
    margin: 0;
    padding: 0;
}

h1#header {
    float: left;
    padding-top: 0px;
    padding-left: 50px;
    border: 10px;
}

h1 > span:first-child:hover {
    border-bottom: 3px solid gray;
}
nav a[href="index.html"]{
    border-radius: 6px 6px 0px 0px;
    border-bottom: 3px solid purple;
    /* width: 1000px; */
    /* text-decoration:none; */
}
/* .selected{
    border-bottom: 3px solid purple;
} */

/* }noclick */
#inav {
    position: fixed;
    top: 0px;
    width: 1920px;
    margin-left: 50;
    padding: 20px;
    /* border: 2px solid; */
    /* border: wheat; */
    border-bottom: 3px solid;
    /* border-radius: 10px; */
    /* background-image: url(/img/mohammad-alizade-341348-unsplash.jpg); */
    background: url(../img/nav.png) center;
    /* background: #528fe99c; */
}
/* #bnav {
    position: fixed;
} */
nav a:link {
    text-decoration: none;
    padding: 3px;
    font-size: 20px
}
/* nav a:visited{
    color: skyblue;
} */
nav a:hover {
    background-color: rgba(75, 199, 236, 0.5);
    font-size: 130%;
    text-decoration: none;
    color: skyblue;
    /* text-decoration: underline; */
    padding: 10px;

    border-radius: 6px 6px 0px 0px;
    border-bottom: 3px solid red;
    width: 1000px;
    text-decoration:none;
}

nav a:active {
    color: red;
}

nav {
    width: 700px;
    /* margin: 50px; */
    margin-left: 250px;
    /* margin-top: 50px; */
   /* padding: 40px;    */  /* 把padding变大才能使得border变大，不能单靠margin */
    padding-top: 15px;
    padding-bottom: 40px;
    border-radius: 40px; 
    /* background: rgba(230, 231, 235, 0.692); */
   /* TODO: CSS3过渡动画 */
   /* background: url(./img/nav.png) no-repeat center; */
   border: solid 1px;
   background-color:white;
}
nav ul {
    padding: 3px;
    margin-left: 40px; 
}
nav li {
    float: left;
    display: block;
    /* list-style-type: none; */
    margin-left: 40px;   /* 防止超链接a元素过近导致浏览器坐标变动选择产生不好的视觉效果 */
    z-index: 1;
}

body {
    font-family: Verdana, sans-serif;
    /* background: url(./img/mohammad-alizade-341348-unsplash.jpg) no-repeat center;
    background-attachment: fixed; */
    
    
    /* background: url(./img/mohammad-alizade-341348-unsplash.jpg) no-repeat; */
    background-size: contain;
    background-attachment: fixed;

    background: white;
    /* background-image:
    linear-gradient(90deg,rgba(0, 0, 0, 0.301) 1px, transparent 0),
    linear-gradient(rgba(0, 0, 0, 0.308) 1px, transparent 0),
    linear-gradient(90deg,hsla(0,0%,100%,0.3) 1px, transparent 0),
    linear-gradient(hsla(0,0%,100%,0.3) 1px, transparent 0);
    background-attachment: fixed;
    background-size: 25px 25px,25px 25px,15px 15px,15px 15px; */
}

aside {
    float: right;
    margin: 30px;
    border-radius: 25px;
    padding-right: 50px;
    padding-left: 50px;
    padding-top: 30px;
    padding-bottom: 30px;
    border: solid 2px gainsboro;
    position: fixed;
    right: 0;
}
aside a:hover{
    color: brown;
}

article {
    margin: 160px 300px 100px 150px;
    /* background-color: rgb(206, 205, 205); */
    /* background-color: rgb(241, 243, 245); */
    background-color: rgba(197, 197, 197, 0.164);
    padding: 30px;
    font-family: 'Trebuchet MS', 'Lucida Sans Unicode', 'Lucida Grande', 'Lucida Sans', Arial, sans-serif;
    background-attachment: unset;
}

/* 
#main {
    margin: 200px 0px 0 0;
    padding: 2px;
    background: yellow;
} */



/*  
#gotop{ 
 display:none;
 font-size: 25px;
 color:#fff;
 text-align: center;
 background: #aaa;
 padding:10px 15px;
 position:fixed;
 right:50px;
 bottom:50px;
 cursor:pointer;   
 }
  */

aside dl dt dd {
    text-decoration: none;
}

footer {
    margin: 30px;
    border: 3px;
    padding: 5px;
    width: 1800px;
    
    /* background-color: rgba(134, 33, 134, 0.548); */
    background-color: #f4f4f4;
    border-top: solid 1px dashed;
    font-size: 1rem;

}

footer ul li {
    float: left;
    display: block;
    padding-left: 20px;
    padding-right: 20px;
    font-size: 12px;
}
#search {
    margin-top: -53px;
    margin-right: 500px;
    padding: 3px;
    float: right;
    border-radius: 30px;
    border: 2px solid rgb(250, 250, 250);
    background-color: #F0EEEE;
    display: flex;
}
#search input{
    outline: none;
    border: none;
    border-radius: 20px;
    padding: 4px 60px 2px 20px; 
}

/* q */
#one {
    margin: 10px;
    padding: 120px;
    border-style:solid;
    border-width: 40px;
    border-color:  rgb(111, 172, 241);
    /* background-image:url(../img/sean-o-406693-unsplash.jpg); */
    background-image: url(../img/massimo-rinaldi-447399-unsplash.jpg);
    background-size:100% 100%;
    background-repeat: no-repeat;
    
}
#two {
    margin: 10px;
    padding:120px;
    border-style:solid;
    border-width: 40px;
    border-color:  rgb(111, 172, 241);
    /* background-image:url(../img/thomas-vimare-111199-unsplash.jpg); */
    background-image: url(../img/david-billings-1516704-unsplash.jpg);
    background-size:100% 100%;
    background-repeat: no-repeat;
    font-size:30px;
}
#three {
    margin: 10px;
    padding:100px 100px;
    border-style:solid;
    border-width: 40px;
    border-color:  rgb(111, 172, 241);
    float: left;
    /* background-image:url(../img/michael-olsen-501079-unsplash.jpg); */
    /* background-image: url(../img/mohammad-metri-421904-unsplash.jpg); */
    background-image: url(../img/3-218.png);
    font-size:36px;
}
#four {
    margin: 10px;
    padding:100px 80px;
    border-style:solid;
    border-width: 40px;
    border-color:  rgb(111, 172, 241);
    float: right;
    /* background-image:url(./img/michael-olsen-501079-unsplash.jpg); */
    background-image: url(../img/4-216.png);
    font-size:36px;
}

#space {
    padding: 250px;
}