body {
    margin: 0;
    font-family: Arial;
    background: #f4f6ff;
}

.header {
    padding: 15px;
    text-align: center;
    background: white;
    font-weight: bold;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.layout {
    display: flex;
}

/* sidebar */
.sidebar {
    width: 220px;
    background: white;
    padding: 10px;
    height: 100vh;
    overflow-y: auto;
}

/* reader */
.reader {
    flex: 1;
    padding: 15px;
}

/* chapter panels */
.panel {
    background: white;
    margin-bottom: 10px;
    padding: 12px;
    border-left: 4px solid #ff4d6d;
    border-radius: 10px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

/* controls */
.controls {
    display: flex;
    gap: 10px;
    margin-bottom: 10px;
}

select, button {
    padding: 8px;
    border-radius: 8px;
    border: 1px solid #ddd;
}

button {
    background: #ff4d6d;
    color: white;
    border: none;
}