当我使用 CSS 单击输入时，有人可以帮助我向标签添加动画吗？-PHP中文网问答

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Formulário | GN</title>
    <link rel="stylesheet" type="text/css" href="style.css">
    <style>
        body{font-family: Arial, Helvetica, sans-serif;
        background-image: linear-gradient(to right, rgb(20, 220, 80), rgb(17, 54, 71));
        }
        .box{
            color: white;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background-color: rgba(0, 0, 0, 0.6);
            padding: 15px;
            border-radius: 15px;
            width: 23%;

        }
        fieldset{
            border: 3px solid greenyellow;    
        }
        legend{
            border: 1px solid greenyellow;    
            padding: 10px;
            text-align: center;
            background-color: greenyellow;
            border-radius: 8px;
            color: black;
        }
        .inputBox{
            position: relative;
        }
        .inputUser{
            background: none;
            border: none;
            border-bottom: 1px solid white;
            outline: none;
            color: white;
            font-size: 14px;
            width: 100%;
            letter-spacing: 2px;
        }
        #submit{
            background-image: linear-gradient(to right, rgb(20, 220, 80), rgb(19, 169, 195));
            width: 40%;
            border: none;
            padding: 10px;
            color: black;
            font-size: 17px;
            cursor: pointer;
            border-radius: 10px;       
            text-align: center;

        }
        #submit1{
            position: relative;
            left: 60px;
            background-image: linear-gradient(to right, rgb(20, 220, 80), rgb(19, 169, 195));
            width: 40%;
            border: none;
            padding: 10px;
            color: black;
            font-size: 17px;
            cursor: pointer;
            border-radius: 10px;  
            text-align: center;
            font-style: inherit;    
           

        }
        #submit:hover{
            background-image: linear-gradient(to right, rgb(20, 220, 80), rgb(7, 105, 40));

        }
        #submit1:hover{
            background-image: linear-gradient(to right, rgb(20, 220, 80), rgb(7, 105, 40));

        }
        .labelInput{
            position: absolute;
            border: none;
            pointer-events: none;
            transition: .5s;
        }
        .inputUser:focus ~.labelInput, 
        .inputUser:valid ~ .labelInput{
            top: -20px;
            font-size: .85px;   
            color: greenyellow;

        }
    </style>
</head>
<body>
   
    <div class="box">
        <from action = "">
            <fieldset> 
                <legend><b>Cadastro de Pacientes</b></legend>
                <br>
                    <div class="inputbox">
                        <label for = "nome" class="labelInput">*<b>Nome:</b></label>
                        <input type="text" name="nome" id="nome" class="inputUser" required>
                    </div>
                    <br><br>
                    <div class="inputbox">
                        <label for ="email" class="labelInput"><b>Email:</b></label>
                        <input type="text" name="email" id="email" class="inputUser" required>                        
                    </div>
                    <br><br>
                   
                    <div class="inputbox">
                        <label for ="telefone" class="labelInput">*<b>Telefone:</b></label>
                        <input type="text" name="telefone" id="telefone" class="inputUser" required>
                    </div>
                    

                    <p>*<b>Sexo:</b></p>
                        <input type="radio" id="feminino" name="genero" value="feminino" required>
                        <label for="feminino">Feminino</label>
                        <br>
                        <input type="radio" id="masculino" name="genero" value="masculino" required>
                        <label for="masculino">Masculino</label>
                        <br><br><br>
                       
                        <div class="inputbox">
                            <label for ="data_nascimento">*<b>Data de Nascimento:</b></label>
                            <input type="date" name="data_nascimento" id="data_nascimento" class="inputUser" required>
                        </div>
                        <br><br>

                        <div class="inputbox">
                            <label for ="cidade" class="labelInput">*<b>Cidade:</b></label>
                            <input type="text" name="cidade" id="cidade" class="inputUser" required>
                        </div>
                        <br><br>

                        <div class="inputbox">
                            <label for ="estado" class="labelInput">*<b>Estado:</b></label>
                            <input type="text" name="estado" id="estado" class="inputUser" required>
                        </div>
                        <br><br>

                        <div class="inputbox">
                            <label for ="endereco" class="labelInput"><b>Endereço:</b></label>
                            <input type="text" name="endereco" id="endereco" class="inputUser" required>
                        </div>
                        <br><br>
                            <a href="file:///home/liniquer/Formul%C3%A1rio%20/pag1.html">
                                <button type="button" name="submit" id="submit" value= "< Voltar">< Voltar</button>
                            </a>    
                            <a href="file:///home/liniquer/Formul%C3%A1rio%20/pag2.html">
                                <button type="button" name="submit" id="submit1" value="Avançar >">Avançar ></button>
                            </a>
            </fieldset>

           
    
</body>
</html>

我尝试在输入中创建一个名为 inputUser 的类，然后我尝试在标签样式中创建动画，但不起作用，我不知道为什么。动画包括当用户点击营地文本时，标签（Nome、Email、Telefone、Cidade、Estado 和 Endereco）上升（顶部：-20px），字体大小减小到 12 px，颜色变为绿黄色。 [[在此处输入图像描述](https://i.stack.imgur.com/8gg3w.png)](https://i.stack.imgur.com/Z05NC.png)

这是通过以下方式完成的：

input:not(:invalid) + label, input:focus + label { top: 0; opacity: 75%; font-size: 0.9rem; background: white; transition: all .2s ease-in-out; }

*{
  font-family: arial;
  padding: 0;
  margin: 0;
}

form {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  
}

.input-field {
  position:relative;
  width:204px;
}

input {
  position: relative;
  
  width: 200px;
  
  margin: 20px;
  padding: 10px 8px;
  
  outline: none;
  border: none;
  border-bottom: 2px  solid black;
  font-size:1rem;
}

input:focus {
  border-bottom: 3px solid black;
}

label {
  position: absolute;
  top: 30%;
  left: 10%;
  
  padding: 5px 10px;
  
  font-size: 1rem;
  
  pointer-events: none;
  transition: all 0.2s ease-in-out 0s;
}

input:not(:invalid) + label,
input:focus + label {
  top: 0;
  
  opacity: 75%;
  font-size: 0.9rem;
  
  background: white;
  
  transition: all .2s ease-in-out;
}

<form>
  <div class="input-field">
    <input type="text" name="forename" required>
    <label>First Name</label>
  </div>

  <div class="input-field">
    <input type="text" name="surname" required>
    <label>Last Name</label>
  </div>
</form>