html,
body {
    padding: 0;
    margin: 0;
    overflow-y: auto;
    height: 100%;
    background: linear-gradient(120deg, #232526 0%, #414345 100%);
    font-family: 'Microsoft YaHei', 'PingFang SC', 'Arial', sans-serif;
}

.back-btn {
    position: fixed;
    top: 18px;
    right: 18px;
    z-index: 1000;
    background: #3498db;
    color: #fff;
    border: none;
    border-radius: 6px;
    padding: 0.4em 1.2em;
    font-size: 0.95em;
    cursor: pointer;
    font-weight: bold;
    box-shadow: 0 2px 8px #0006;
}

.qtspinner center {
    margin-top: 2em;
    line-height: 150%;
}

.qtstatus {
    color: #fff;
    font-size: 1.2em;
    margin-bottom: 1em;
}

.loader {
    border: 8px solid #f3f3f3;
    border-top: 8px solid #3498db;
    border-radius: 50%;
    width: 60px;
    height: 60px;
    animation: spin 1s linear infinite;
    margin: 0 auto 1em auto;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }

    100% {
        transform: rotate(360deg);
    }
}

#screen {
    width: 1600px;
    height: 900px;
    margin: 20px auto;
}