33% {background:url("../img/2.jpg");} 67% {background:url("../img/3.jpg");} 100% {background:url("../img/1.jpg");}什么意思

这是一个CSS3动画关键帧（keyframes）的设置语法，表示元素在不同时间点的样式。具体地说，这里的33%、67%和100%分别表示动画进行到了33%、67%和100%时的状态。{background:url("../img/2.jpg");}、{background:url("../img/3.jpg");}和{background:url("../img/1.jpg");}分别表示元素在33%、67%和100%时的样式，即背景图片分别为2.jpg、3.jpg和1.jpg。

这样设置的动画效果可能是：元素从开始状态（背景图片为1.jpg）开始，经过33%的时间后，背景图片变为2.jpg；再经过34%（即总时间的33%至67%）的时间后，背景图片变为3.jpg；最后经过33%（即总时间的67%至100%）的时间后，背景图片又回到了1.jpg。这样的动画可以循环播放，直到停止或被取消。

相关问题

主目录为D:\NMT16\Web\content，background-image: url("../../img/course.jpg"); background-image: url("./images/newCourse.png"); background-image: url("file:///D:/NMT16/css/images/exp.png"); 分析以上代码的意义， 比较三行代码中路径的差异， 并写出"course. jpg" 、 "newCourse.png"、"exp.png"所在文件夹位置。

以上代码中，三行代码中的路径分别为相对路径、相对路径和绝对路径。

第一行代码中的路径 "../../img/course.jpg" 表示该图片文件位于当前CSS文件的上两级目录下的 img 文件夹中。

第二行代码中的路径 "./images/newCourse.png" 表示该图片文件位于当前CSS文件所在的同级目录下的 images 文件夹中。

第三行代码中的路径 "file:///D:/NMT16/css/images/exp.png" 表示该图片文件位于绝对路径 D:\NMT16\css\images\exp.png 中。

因此，"course.jpg" 位于 D:\NMT16\Web\img 文件夹中，"newCourse.png" 位于 D:\NMT16\Web\content\images 文件夹中，"exp.png" 位于 D:\NMT16\css\images 文件夹中。

优化下面代码.bg { width: 100%; height: 100vh; background-image: url('../../assets/img/info-bg.png'); background-size: 100% 100%; background-repeat: no-repeat; position: relative; font-family: AlibabaPuHuiTiR; .goBack { position: absolute; top: 34px; right: 65px; cursor: pointer; color: #ffffff; width: 181px; padding: 15px 10px; background: rgba(24, 31, 30, 0.52); border: 1px solid #4a524e; border-radius: 5px; font-size: 18px; font-family: AlibabaPuHuiTiR; z-index: 111; display: flex; flex-direction: row; justify-content: space-between; align-items: center; } .home-left { position: absolute; top: 18%; left: 40px; width: 41%; height: 76%; font-size: 24px; color: #ffffff; } .unit { font-size: 24px; color: #636363; } .home-left-title { font-size: 24px; color: #ffffff; line-height: 36px; } .home-right { position: absolute; top: 18%; right: 88px; width: 46%; height: 78%; } .model { display: flex; justify-content: center; align-items: center; height: 90%; } #threeContained { width: 100%; height: 100%; } .model-qk-img { width: 82%; height: 90%; background-image: url('../../assets/img/howo.png'); background-size: 100% 100%; background-repeat: no-repeat; } .model-zk-img { width: 56%; height: 90%; background-image: url('../../assets/img/heavyT.png'); background-size: 100% 100%; background-repeat: no-repeat; } .model-gj-img { width: 82%; height: 90%; background-image: url('../../assets/img/transit.png'); background-size: 100% 100%; background-repeat: no-repeat; } .car-online { margin-bottom: 50px; } } .day-data { display: flex; flex-direction: row; justify-content: space-between; align-items: center; height: 29%; margin-left: 30px; } .day-val { width: 40%; } .prefix { display: inline-block; width: 6px; height: 14px; background: #ffffff; margin-right: 20px; } .zh-title { margin-left: 30px; padding-top: 30px; font-size: 30px; font-weight: 700; text-align: left; color: #ffffff; line-height: 32px; letter-spacing: 0.3px; font-family: AlibabaPuHuiTiB; } .en-title { margin-left: 30px; font-size: 14px; font-weight: 400; text-align: left; color: #ffffff; line-height: 32px; letter-spacing: -0.91px; font-family: AlibabaPuHuiTiR; }

Here are some suggestions to optimize the code:

1. Use shorthand properties whenever possible. For example, instead of writing `background-size: 100% 100%;`, you can write `background-size: cover;`.

2. Consolidate similar styles into classes, instead of repeating them for every element. For example, you can create a class for the font family and apply it to all elements that use that font.

3. Remove unnecessary styles that are not being used or overwritten by other styles.

4. Use more specific selectors to target elements, instead of relying on the order of elements in the HTML. This will make the code more robust and easier to maintain.

5. Consider using a CSS preprocessor like Sass or Less, which can help you write cleaner and more organized code.

Here's an example of how the code could be optimized:

.bg {
  width: 100%;
  height: 100vh;
  background: url('../../assets/img/info-bg.png') no-repeat center center / cover;
  position: relative;
  font-family: AlibabaPuHuiTiR;
}

.goBack {
  position: absolute;
  top: 34px;
  right: 65px;
  cursor: pointer;
  color: #fff;
  width: 181px;
  padding: 15px 10px;
  background: rgba(24, 31, 30, 0.52);
  border: 1px solid #4a524e;
  border-radius: 5px;
  font-size: 18px;
  font-family: AlibabaPuHuiTiR;
  z-index: 111;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  align-items: center;
}

.home-left {
  position: absolute;
  top: 18%;
  left: 40px;
  width: 41%;
  height: 76%;
  font-size: 24px;
  color: #fff;
}

.unit {
  font-size: 24px;
  color: #636363;
}

.home-left-title {
  font-size: 24px;
  color: #fff;
  line-height: 36px;
}

.home-right {
  position: absolute;
  top: 18%;
  right: 88px;
  width: 46%;
  height: 78%;
}

.model {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 90%;
}

#threeContained {
  width: 100%;
  height: 100%;
}

.model-qk-img {
  width: 82%;
  height: 90%;
  background: url('../../assets/img/howo.png') no-repeat center center / cover;
}

.model-zk-img {
  width: 56%;
  height: 90%;
  background: url('../../assets/img/heavyT.png') no-repeat center center / cover;
}

.model-gj-img {
  width: 82%;
  height: 90%;
  background: url('../../assets/img/transit.png') no-repeat center center / cover;
}

.car-online {
  margin-bottom: 50px;
}

.day-data {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 29%;
  margin-left: 30px;
}

.day-val {
  width: 40%;
}

.prefix {
  display: inline-block;
  width: 6px;
  height: 14px;
  background: #fff;
  margin-right: 20px;
}

.zh-title {
  margin-left: 30px;
  padding-top: 30px;
  font-size: 30px;
  font-weight: 700;
  text-align: left;
  color: #fff;
  line-height: 32px;
  letter-spacing: 0.3px;
  font-family: AlibabaPuHuiTiB;
}

.en-title {
  margin-left: 30px;
  font-size: 14px;
  font-weight: 400;
  text-align: left;
  color: #fff;
  line-height: 32px;
  letter-spacing: -0.91px;
  font-family: AlibabaPuHuiTiR;
}

.font-alibaba {
  font-family: AlibabaPuHuiTiR;
}

.font-alibaba-bold {
  font-family: AlibabaPuHuiTiB;
}