:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --success: #16a34a;
    --warning: #ca8a04;
    --danger: #dc2626;
    --bg-color: #f8fafc;
    --text-color: #1e293b;
    --card-bg: #ffffff;
    --border-color: #e2e8f0;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: var(--primary);
    color: white;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 1.25rem;
}

header nav a {
    color: white;
    text-decoration: none;
    margin-left: 1rem;
    font-weight: 500;
    transition: opacity 0.2s;
}

header nav a:hover {
    opacity: 0.8;
}

main {
    flex: 1;
    padding: 2rem;
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
}

footer {
    background-color: #1e293b;
    color: #94a3b8;
    text-align: center;
    padding: 1rem;
    font-size: 0.875rem;
}

.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    margin-bottom: 1.5rem;
}

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 6px;
    background-color: var(--primary);
    color: white;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    text-align: center;
    transition: background-color 0.2s;
}

.btn:hover {
    background-color: var(--primary-dark);
}

.btn-success { background-color: var(--success); }
.btn-success:hover { background-color: #15803d; }
.btn-danger { background-color: var(--danger); }
.btn-danger:hover { background-color: #b91c1c; }

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-group input, .form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
    background: white;
    border-radius: 8px;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

th, td {
    padding: 0.75rem 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

th {
    background-color: #f1f5f9;
    font-weight: 600;
}

.alert {
    padding: 0.75rem 1rem;
    border-radius: 6px;
    margin-bottom: 1rem;
    font-size: 0.9rem;
}
.alert-success { background-color: #dcfce7; color: #166534; }
.alert-error { background-color: #fee2e2; color: #991b1b; }

@media (max-width: 768px) {
    main { padding: 1rem; }
    header { flex-direction: column; gap: 0.5rem; text-align: center; }
    header nav { margin-top: 0.5rem; }
}