body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: #f8f9fa;
    color: #333;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    background-color: #fff;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    padding: 1rem 0;
    margin-bottom: 2rem;
}

nav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 20px;
}

nav a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
}

.card {
    background: #fff;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    padding: 20px;
    margin-bottom: 20px;
}

.btn {
    display: inline-block;
    padding: 8px 16px;
    border-radius: 4px;
    text-decoration: none;
    cursor: pointer;
    border: none;
    font-size: 14px;
}

.btn-primary {
    background-color: #007bff;
    color: #fff;
}

.btn-danger {
    background-color: #dc3545;
    color: #fff;
}

.form-group {
    margin-bottom: 15px;
}

label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
}

input[type="text"],
input[type="password"],
input[type="number"],
select,
textarea {
    width: 100%;
    padding: 8px;
    border: 1px solid #ddd;
    border-radius: 4px;
    box-sizing: border-box;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

th {
    background-color: #f8f9fa;
}

.alert {
    padding: 10px;
    border-radius: 4px;
    margin-bottom: 15px;
}

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

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