:root {
    --primary-color: #3498db;
    --primary-dark: #2980b9;
    --dark-gray: #2c3e50;
    --darker-gray: #1a252f;
    --light-gray: #7f8c8d;
    --lighter-gray: #ecf0f1;
    --success-color: #2ecc71;
    --error-color: #e74c3c;
}

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

body {
    background-color: var(--dark-gray);
    color: var(--lighter-gray);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 20px;
    position: relative;
}

.sidebar {
    position: fixed;
    left: 20px;
    top: 20px;
    z-index: 100;
}

.menu-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    padding: 10px 15px;
    font-size: 20px;
    cursor: pointer;
    transition: background-color 0.3s;
}

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

.menu-content {
    display: none;
    position: absolute;
    background-color: var(--darker-gray);
    min-width: 160px;
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
    border-radius: 4px;
    z-index: 1;
    left: 0;
    top: 45px;
}

.menu-content a {
    color: var(--lighter-gray);
    padding: 12px 16px;
    text-decoration: none;
    display: block;
    transition: background-color 0.3s;
}

.menu-content a:hover {
    background-color: var(--dark-gray);
}

.container {
    max-width: 800px;
    width: 100%;
    background-color: var(--darker-gray);
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    margin-top: 20px;
}

h1 {
    text-align: center;
    margin-bottom: 30px;
    color: var(--primary-color);
}

.version {
    font-size: 16px;
    color: var(--light-gray);
}

.file-selector {
    margin-bottom: 20px;
    display: flex;
    align-items: center;
}

.select-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    padding: 12px 20px;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
    flex-shrink: 0;
}

.audio-btn {
    background-color: #9b59b6;
}

.audio-btn:hover {
    background-color: #8e44ad;
}

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

.file-name {
    margin-left: 15px;
    color: var(--light-gray);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.action-area {
    margin-top: 30px;
}

.merge-btn {
    background-color: var(--success-color);
    color: white;
    border: none;
    border-radius: 4px;
    padding: 12px 20px;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
    width: 100%;
    margin-bottom: 20px;
}

.merge-btn:hover {
    background-color: #27ae60;
}

.merge-btn:disabled {
    background-color: var(--light-gray);
    cursor: not-allowed;
}

.log-container {
    width: 100%;
}

.log-container textarea {
    width: 100%;
    height: 200px;
    padding: 15px;
    border-radius: 4px;
    border: 1px solid var(--dark-gray);
    background-color: #34495e;
    color: var(--lighter-gray);
    resize: none;
    font-family: monospace;
    font-size: 14px;
}

.download-area {
    margin-top: 20px;
    text-align: center;
}

.download-btn {
    display: inline-block;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    padding: 12px 20px;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
    text-decoration: none;
}

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

.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    overflow: auto;
}

.modal-content {
    background-color: var(--darker-gray);
    margin: 15% auto;
    padding: 25px;
    border-radius: 8px;
    width: 80%;
    max-width: 500px;
    position: relative;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.close-btn {
    color: var(--light-gray);
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    transition: color 0.3s;
}

.close-btn:hover {
    color: var(--lighter-gray);
}

.modal-content h2 {
    color: var(--primary-color);
    margin-bottom: 15px;
}

.modal-content p {
    margin-bottom: 10px;
    line-height: 1.6;
}

@media (max-width: 600px) {
    .container {
        padding: 20px;
    }
    
    .file-selector {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .file-name {
        margin-left: 0;
        margin-top: 10px;
    }
}