Why my app.css does not want to show the result?

I have an HTML page (chat.blade.php) and a CSS file (app.css), and for some reason, my CSS code does not change the page after the PHP run dev command, maybe I did not write the path correctly in the HTML file, please tell me because the first once I work with CSS. app.css (in resources folder)

@import 'tailwindcss/base';
@import 'tailwindcss/components';
@import 'tailwindcss/utilities';

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;

    font-family: 'Bicyclette', sans-serif;
}

body {
    background-color: #EEE;
}

input, button {
    appearance: none;
    border: none;
    outline: none;
    background: none;
}

input {
    display: block;
    width: 100%;
    background-color: #FFF;
    padding: 12px 16px;

    font-size: 18px;
    color: #888;
}

.app {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

header {
    display: flex;
    padding-top: 128px;
    padding-bottom: 32px;
    background-color: #8C38FF;
    background-image: linear-gradient(to bottom, #8C38FF, #6317ce);
    align-items: center;
    justify-content: flex-end;
    flex-direction: column;
    box-shadow: 0px 6px 12px rgba(0, 0 ,0 , 0.15);
    padding-left: 16px;
    padding-right: 16px;
}

h1 {
    color: #FFF;
    text-transform: uppercase;
    text-align: center;
    margin-bottom: 16px;
}

#username {
    border-radius: 8px;
    transition: 0.4s;
    text-align: center;
}

#username:focus {
    box-shadow: 0px 6px 12px rgba(0, 0, 0, 0.25);
}

#messages {
    flex: 1 1 0%;
    overflow: scroll;
    padding: 16px;
}

.message {
    display: block;
    width: 100%;
    border-radius: 99px;
    background-color: #FFF;
    padding: 8px 16px;
    box-shadow: 0px 6px 12px rgba(0, 0, 0, 0.15);
    font-weight: 400;
    margin-bottom: 16px;
}

.message strong {
    color: #8C38FF;
    font-weight: 600;
}

#message_form {
    display: flex;
}

#message_input {
    flex: 1 1 0%;
}

#message_send {
    appearance: none;
    background-color: #8C38FF;
    padding: 4px 8px;
    color: #FFF;
    text-transform: uppercase;
}

and my chat.blade.php

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Чат</title>

    <link rel="stylesheet" href="./css/app.css">
</head>
<body>
    <div class="app">
        <header>
        <h1>Чат</h1>
            <input type="text" name="username" id="username" placeholder="Вкажіть ваше ім'я">
        </header>

        <div id="messages"></div>

        <form id="message_form">
            <input type="text" name="message" id="message_input" placeholder="Написати повідомлення...">
            <button type="submit" id="message_send">Отправить сообщение</button>
        </form>
    </div>

<script src="./js/app.js"></script>
</body>
</html>

Answer

You should update your CSS path file to ../../public/css/app.css

../: means go to previous folder from the current position (here is chat.blade.php)