:root {
    --background-color: #121212;
    --surface-color: #1E1E1E;
    --primary-color: #3A86FF;
    --primary-hover-color: #5A9BFF;
    --text-color: #E0E0E0;
    --text-secondary-color: #A0A0A0;
    --border-color: #333333;
    --success-color: #4CAF50;
    --error-color: #F44336;

    /* Light Mode Variables */
    --lm-background-color: #F5F5F5;
    --lm-surface-color: #FFFFFF;
    --lm-text-color: #121212;
    --lm-text-secondary-color: #555555;
    --lm-border-color: #E0E0E0;
}

body.light-mode {
    --background-color: var(--lm-background-color);
    --surface-color: var(--lm-surface-color);
    --text-color: var(--lm-text-color);
    --text-secondary-color: var(--lm-text-secondary-color);
    --border-color: var(--lm-border-color);
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    margin: 0;
    line-height: 1.6;
    font-size: 16px;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

.main-header {
    background-color: var(--surface-color);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 33px;
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
}

.nav-brand i {
    margin-right: 8px;
}

.nav-menu {
    list-style: none;
    display: flex;
    align-items: center;
    gap: 25px;
    margin: 0;
    padding: 0;
}

.nav-link {
    color: var(--text-secondary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-link:hover, .nav-link.active {
    color: var(--text-color);
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-secondary-color);
    cursor: pointer;
    font-size: 1.2rem;
    padding: 5px;
    margin-left: -10px; /* Adjust position */
}

.theme-toggle:hover {
    color: var(--text-color);
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 1.5rem;
    cursor: pointer;
}

.tts-app-section {
    padding: 4rem 0;
}

.tts-app-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    background-color: var(--surface-color);
    padding: 40px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.tts-form h1 {
    font-size: 2rem;
    margin-top: 0;
}

.tts-form p {
    color: var(--text-secondary-color);
    margin-bottom: 30px;
}

.form-row {
    display: flex;
    gap: 20px;
    margin-bottom: 20px;
}

.form-group {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.form-group label {
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-secondary-color);
}

select, textarea {
    width: 100%;
    background-color: var(--background-color);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 12px;
    font-family: 'Inter', sans-serif;
    font-size: 1rem;
    box-sizing: border-box;
}

select:disabled {
    opacity: 0.5;
}

textarea {
    min-height: 150px;
    resize: vertical;
}

#char-count {
    text-align: right;
    font-size: 0.8rem;
    color: var(--text-secondary-color);
    margin-top: 5px;
}

.button-primary {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    padding: 14px 20px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s ease;
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
}

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

.button-primary:disabled {
    background-color: #555;
    cursor: not-allowed;
}

.tts-results {
    background-color: var(--background-color);
    padding: 30px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.tts-results h2 {
    margin-top: 0;
    color: var(--text-secondary-color);
}

.audio-container {
    width: 100%;
}

#audio-player {
    width: 100%;
    margin-bottom: 20px;
}

.download-btn {
    display: inline-block;
    background-color: transparent;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
    border-radius: 8px;
    padding: 12px 20px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
}

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

.loading {
    display: none;
    text-align: center;
    margin-top: 20px;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.spinner {
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top: 4px solid var(--primary-color);
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
    margin: 0 auto 10px;
}
@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.error-message, .success-message {
    display: none;
    margin-top: 15px;
    padding: 10px;
    border-radius: 5px;
    text-align: center;
    color: white;
}
.error-message { background-color: var(--error-color); }
.success-message { background-color: var(--success-color); }


.main-footer {
    background-color: var(--surface-color);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
    margin-top: 4rem;
    text-align: center;
}

.footer-links {
    list-style: none;
    padding: 0;
    margin: 0 0 1rem 0;
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

.footer-links a {
    color: var(--text-secondary-color);
    text-decoration: none;
}

.footer-links a:hover {
    color: var(--text-color);
}

.footer-bottom p {
    color: var(--text-secondary-color);
    font-size: 0.9rem;
    margin: 0;
}

@media (max-width: 768px) {
    .nav-menu {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 65px;
        left: 0;
        width: 100%;
        background-color: var(--surface-color);
        border-top: 1px solid var(--border-color);
        padding: 1rem 0;
        gap: 0;
    }

    .nav-menu.active {
        display: flex;
    }

    .nav-menu li {
        text-align: center;
    }

    .nav-link {
        display: block;
        padding: 0.8rem 0;
        width: 100%;
    }

    .nav-toggle {
        display: block;
    }

    .tts-app-grid {
        grid-template-columns: 1fr;
    }

    .theme-toggle-li {
        padding: 0.5rem 0;
    }
}