:root {
    --bg: #ffffff;
    --text: #1a1a1a;
    --header-bg: #f8f9fa;
    --accent: #3498db;
    --border: #ddd;
}

body.dark-mode {
    --bg: #121212;
    --text: #e0e0e0;
    --header-bg: #1f1f1f;
    --border: #333;
}

body {
    background-color: var(--bg);
    color: var(--text);
    font-family: 'Georgia', serif;
    margin: 0;
    line-height: 1.8;
    transition: background 0.3s, color 0.3s;
}

#main-header {
    position: sticky;
    top: 0;
    background: var(--header-bg);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    padding: 10px 20px;
}

.header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
}

.selectors-area {
    display: flex;
    gap: 10px;
    align-items: center;
}

.logo-area { display: flex; align-items: center; gap: 10px; }
h1 { font-size: 1.2rem; margin: 0; }

.reader-controls button {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text);
    padding: 5px 10px;
    cursor: pointer;
    border-radius: 4px;
    margin-left: 5px;
}

select {
    padding: 6px;
    border-radius: 4px;
    border: 1px solid var(--border);
    background: var(--bg);
    color: var(--text);
}

#content-area {
    max-width: 750px;
    margin: 0 auto;
    padding: 40px 20px;
}

/* Tamaños de fuente */
.font-small { font-size: 16px; }
.font-medium { font-size: 19px; }
.font-large { font-size: 23px; }

.chapter {
    margin-bottom: 80px;
}

.chapter-header {
    border-bottom: 2px solid var(--accent);
    padding-bottom: 10px;
    margin-bottom: 30px;
}

.loader {
    text-align: center;
    margin-top: 50px;
    font-style: italic;
}

/* Resaltado de lectura */
.reading-paragraph {
    background-color: rgba(52, 152, 219, 0.15); /* Azul muy tenue */
    border-radius: 4px;
    transition: background-color 0.3s ease;
}

/* Animación simple para el botón cuando está activo */
#tts-btn.active {
    background-color: #e74c3c;
    color: white;
}