用css画加号减号

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Plus Sign</title>
    <style>
        .plus-sign {
            width: 20px;
            height: 20px;
            border: 2px solid black;
            border-radius: 50%;
            position: relative;
        }
        .plus-sign::before {
            content: '';
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 10px;
            height: 2px;
            background-color: black;
        }
        .plus-sign::after {
            content: '';
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%) rotate(90deg);
            width: 10px;
            height: 2px;
            background-color: black;
        }
    </style>
</head>
<body>
    <div class="plus-sign"></div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Minus Sign</title>
    <style>
        .minus-sign {
            width: 20px;
            height: 2px;
            background-color: black;
            position: relative;
        }
    </style>
</head>
<body>
    <div class="minus-sign"></div>
</body>
</html>