body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    font-family: "Microsoft YaHei", "微软雅黑", sans-serif;
    color: #fff;
    overflow: hidden;
}

.background-video {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -2;
}

.background-video img {
    display: block;
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.4);
    z-index: -1;
}

.container {
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding-bottom: 60px;
    box-sizing: border-box;
}

.top-space {
    flex: 1;
}

.bottom-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    text-align: center;
}

.title {
    font-size: 30px;
    font-weight: bold;
    margin-bottom: 35px;
    text-shadow: 2px 2px 8px rgba(0,0,0,0.8);
}

.idioms {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
    max-width: 800px;
    width: 90%;
    margin-bottom: 50px;
    font-size: 21px;
    text-shadow: 1px 1px 6px rgba(0,0,0,0.8);
}

.app-download {
    padding: 14px 50px;
    font-size: 24px;
    font-weight: bold;
    color: #fff;
    background: linear-gradient(to right, #ffd700, #ff8c00);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    box-shadow: 0 8px 20px rgba(0,0,0,0.4);
    transition: transform 0.3s;
}

.app-download:hover {
    transform: scale(1.05);
}

.app-download:active {
    transform: scale(0.98);
}

@media (max-width: 768px) {
    .container {
        padding-bottom: 50px;
    }
    .title {
        font-size: 26px;
        margin-bottom: 30px;
    }
    .idioms {
        font-size: 18px;
        gap: 10px;
        margin-bottom: 45px;
    }
    .app-download {
        padding: 12px 45px;
        font-size: 22px;
    }
}