:root {
    --primary-color: #007BFF;
    --primary-hover: #0056b3;
    --bg-color: #f7f9fc;
    --text-color: #333;
    --border-color: #d1d9e6;
    --drop-zone-bg: #fff;
    --footer-bg: #eef2f7;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}
main {
    flex-grow: 1;
    padding: 20px 0;
}
.container {
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
    padding: 0 20px;
    text-align: center;
}

/* Header and Footer */
.site-header, .site-footer {
    padding: 20px 0;
}
.site-header {
    border-bottom: 1px solid var(--border-color);
}
.site-title {
    margin: 0;
    font-size: 1.8em;
    color: var(--primary-color);
}
.site-footer {
    background-color: var(--footer-bg);
    color: #666;
    font-size: 0.9em;
    border-top: 1px solid var(--border-color);
}
.site-footer p {
    margin: 0;
}

/* Language Switcher */
.lang-switcher {
    margin-bottom: 20px;
    text-align: right;
}
.lang-switcher button {
    background: none;
    border: 1px solid var(--border-color);
    padding: 5px 10px;
    border-radius: 6px;
    cursor: pointer;
    font-weight: bold;
}
.lang-switcher button.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* Drop Zone */
#drop-zone {
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    padding: 40px 30px;
    background-color: var(--drop-zone-bg);
    transition: all 0.3s ease;
    cursor: pointer;
}
#drop-zone.dragover {
    border-color: var(--primary-color);
    background-color: #e9f5ff;
}
#file-input { display: none; }
.browse-btn { color: var(--primary-color); font-weight: bold; }

/* Controls */
.controls {
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    margin-top: 20px;
    text-align: left;
    border: 1px solid var(--border-color);
}
.quality-control {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.quality-control label { font-weight: bold; }
.quality-control input[type="range"] { flex-grow: 1; margin: 0 15px; }

/* Results */
.results { margin-top: 20px; text-align: left; opacity: 0; transform: translateY(20px); transition: all 0.5s ease; visibility: hidden; }
.results.visible { opacity: 1; transform: translateY(0); visibility: visible; }
.result-item { background-color: #fff; padding: 15px; border-radius: 8px; border: 1px solid var(--border-color); margin-bottom: 10px; }
.result-item span { font-weight: bold; color: var(--primary-color); }
#download-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 12px 20px;
    font-size: 1.1em;
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
    width: 100%;
    margin-top: 10px;
    transition: background-color 0.3s ease;
}
#download-btn:hover { background-color: var(--primary-hover); }
#download-btn:disabled { background-color: #a0cffa; cursor: not-allowed; }