:root {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
    --primary-color: #3498db;
    --secondary-color: #2c3e50;
    --accent-color: #e74c3c;
    --border-color: #444;
    --card-bg: #2d2d2d;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --spacing-md: 1rem;
    --spacing-sm: 0.5rem;
}

body {
    margin: 0;
    padding: 0;
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

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

.app-header {
    background-color: var(--secondary-color);
    padding: var(--spacing-md);
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    box-shadow: var(--shadow);
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-right: var(--spacing-md);
}

.main-nav {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.nav-btn {
    background: none;
    border: none;
    color: var(--text-color);
    padding: var(--spacing-sm) var(--spacing-md);
    cursor: pointer;
    border-radius: 4px;
    transition: background-color 0.2s;
    font-size: 1rem;
}

.nav-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.nav-btn.active {
    background-color: var(--primary-color);
    color: white;
}

.tab-content {
    flex: 1;
    padding: var(--spacing-md);
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
    box-sizing: border-box;
}

.tab-pane {
    display: none; /* Hidden by default */
}

.tab-pane.active {
    display: block; /* Shown when active */
    animation: fadeIn 0.3s ease-in-out;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.app-footer {
    text-align: center;
    padding: var(--spacing-md);
    background-color: var(--secondary-color);
    font-size: 0.9rem;
    color: #aaa;
}

/* Utilities */
.card {
    background-color: var(--card-bg);
    border-radius: 8px;
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    box-shadow: var(--shadow);
}

.btn {
    padding: 0.6rem 1.2rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1rem;
}

.btn:hover {
    filter: brightness(1.1);
}

.btn-secondary {
    background-color: var(--secondary-color);
}

.form-group {
    margin-bottom: var(--spacing-md);
}

label {
    display: block;
    margin-bottom: var(--spacing-sm);
    font-weight: bold;
}

input, select, textarea {
    width: 100%;
    padding: 0.6rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: #333;
    color: white;
    box-sizing: border-box;
}

input:focus, select:focus, textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}