* {
    box-sizing: border-box;
}
body {
    margin: 0;
    font-family: 'Segoe UI', sans-serif;
    background-color: #f4f6f8;
}

.sidebar {
    width: 220px;
    background-color: #222;
    position: fixed;
    height: 100vh;
    color: white;
}

.sidebar h2 {
    text-align: center;
    padding: 15px;
    background-color: #111;
    font-size: 22px;
}

.sidebar a {
    display: flex;
    align-items: center;
    padding: 14px 20px;
    color: white;
    text-decoration: none;
    border-bottom: 1px solid #333;
    transition: background 0.3s;
}

.sidebar a i {
    margin-right: 10px;
}

.sidebar a:hover {
    background-color: #444;
}

.main {
    margin-left: 220px;
    padding: 30px;
}

.form-container {
    background-color: white;
    padding: 30px;
    border-radius: 10px;
    max-width: 800px;
    margin: auto;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

h3 {
    text-align: center;
    margin-bottom: 20px;
}

input[type="text"],
input[type="number"],
textarea,
select {
    width: 100%;
    padding: 12px;
    margin: 8px 0 20px;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 16px;
}

input[type="file"] {
    margin-bottom: 10px;
}

.thumbnail-preview {
    width: 150px;
    display: none;
    margin-bottom: 20px;
}

button {
    background-color: #28a745;
    color: white;
    border: none;
    padding: 12px 28px;
    font-size: 16px;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.3s ease;
}

button:hover {
    background-color: #218838;
}

.success, .error {
    padding: 12px;
    border-radius: 6px;
    margin-bottom: 20px;
    font-weight: bold;
    text-align: center;
}

.success {
    background-color: #d4edda;
    color: #155724;
}

.error {
    background-color: #f8d7da;
    color: #721c24;
}

@media screen and (max-width: 768px) {
    .sidebar {
        width: 100%;
        height: auto;
        position: relative;
    }

    .main {
        margin-left: 0;
        padding: 15px;
    }
}