如何用 CSS 做一個圓環
隨著現代網頁設計的不斷進步，我們越來越需要使用 CSS 來創建各種不同類型的圖形和布局。今天，我們將探討如何使用 CSS 創建一個圓環，這是一個經典的網頁設計元素。
首先，我們需要了解圓環的形狀和大小。圓環的形狀是一個內圓和兩個外圓，它們的半徑相等。我們可以使用 CSS 的 `border-radius` 屬性來設置內圓和外圓的半徑，然后使用 `border` 屬性來設置圓環的邊緣。
下面是一個使用 CSS 創建一個基本圓環的示例：
```html
<div style="width: 100px; height: 100px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border: 2px solid black;">
<div style="width: 50px; height: 50px;border-radius: 50%;border:2px solid black;">
<div style="width: 50px;height:50px;border-radius:50%;