.captcha-bg-container {
    position: relative;
    width: 100%;
    max-width: 300px;
    margin: 0 auto;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}
.captcha-track {
    position: relative;
    background: #f0f2f5;
    border-radius: 30px;
    margin-top: 12px;
    height: 36px;
    width: 100%;
    max-width: 300px;
    margin-left: auto;
    margin-right: auto;
    cursor: pointer;
}
.captcha-bar {
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    background: #3498db;
    border-radius: 30px;
    width: 0%;
    transition: width 0.05s linear;
}
.captcha-handle {
    position: absolute;
    left: 0;
    top: 0;
    width: 36px;
    height: 36px;
    background: white;
    border-radius: 50%;
    box-shadow: 0 2px 6px rgba(0,0,0,0.2);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    cursor: grab;
    z-index: 2;
    touch-action: none;      /* 阻止触摸时浏览器滚动/缩放 */
    user-select: none;       /* 避免拖动时选中文本 */
    -webkit-tap-highlight-color: transparent;
}
.captcha-handle:active { cursor: grabbing; }
.captcha-message {
    text-align: center;
    font-size: 12px;
    margin-top: 8px;
    min-height: 20px;
}
.captcha-refresh {
    text-align: center;
    font-size: 18px;
    cursor: pointer;
    margin-top: 8px;
    color: #666;
}
.captcha-refresh:hover { color: #3498db; }
@media (max-width: 640px) {
    .captcha-bg-container, .captcha-track { max-width: 260px; }
    .captcha-handle { width: 32px; height: 32px; }
}