* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { width: 100%; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: linear-gradient(to bottom, #E4EEF6 0%, #C9DDF4 100%);
    background-attachment: fixed;
    min-height: 100vh;
    display: flex; flex-direction: column; align-items: center;
    padding-bottom: 48px;
}

/* ── 顶部标题栏 ── */
.nav-bar {
    width: 100%; height: 52px;
    background: rgba(228, 238, 246, .5);                                /* 半透明：透出顶部背景图 */
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);  /* 毛玻璃：更朦胧，标题仍清晰 */
    display: flex; align-items: center; padding: 0 16px; gap: 10px;
    position: sticky; top: 0; z-index: 100; flex-shrink: 0;
}
.nav-back {
    font-size: 24px; color: #2B3A4A; line-height: 1;
    padding: 4px 6px 4px 0; cursor: pointer; flex-shrink: 0;
}
.nav-icon {
    width: 28px; height: 28px; border-radius: 7px; flex-shrink: 0;
}
.nav-title {
    margin-left: auto;
    font-size: 16px; font-weight: 600; color: #2B3A4A;
}

/* ── 顶部 Hero ── */
.hero {
    width: 100%;     /* 不定位：背景图改为相对页面顶部定位，从最顶端开始 */
}
.hero-bg {
    position: absolute; top: 0; left: 0; z-index: -1;   /* 相对页面顶部：从最顶端开始，内容叠在其上 */
    width: 70%; pointer-events: none;
    mix-blend-mode: multiply;            /* 白底融进页面蓝色背景，只留柔和线条 */
    -webkit-mask-image: radial-gradient(150% 150% at 0 0, #000 30%, transparent 78%);
            mask-image: radial-gradient(150% 150% at 0 0, #000 30%, transparent 78%);
}
.hero-logo {
    width: 80px; height: 80px; border-radius: 20px;
    margin-top: 38px; z-index: 1;
    box-shadow: 0 4px 18px rgba(0,0,0,.18);
}

/* ── 通用 section ── */
.page-section {
    width: 100%; display: flex; flex-direction: column;
    align-items: center; margin-top: 38px;
}

/* ── 核心功能图标 ── */
.feat-title {
    font-size: 26px; font-weight: 900; color: #2B3A4A;
    letter-spacing: 2px; margin-bottom: 22px;
    display: flex; align-items: center; justify-content: center; gap: 12px;
    width: 92%; max-width: 480px;
}
.feat-title-dash {
    flex: 1; max-width: 52px; height: 2px;
    border-radius: 2px; position: relative; flex-shrink: 0;
}
.feat-title > .feat-title-dash:first-child {
    background: linear-gradient(to right, transparent, rgba(58,126,228,.65));
}
.feat-title > .feat-title-dash:last-child {
    background: linear-gradient(to left, transparent, rgba(58,126,228,.65));
}
.feat-title-text {
    background: linear-gradient(135deg, #2c6fe0 0%, #9333ea 100%);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
}
.feat-cards {
    display: flex; gap: 12px; width: 92%; max-width: 480px;
}
.feat-card {
    flex: 1; background: #fff; border-radius: 20px;
    box-shadow: 0 6px 22px rgba(43,58,74,.11);
    padding: 26px 8px 22px;
    display: flex; flex-direction: column; align-items: center; gap: 14px;
}
.feat-card-icon {
    display: flex; align-items: center; justify-content: center;
    flex-shrink: 0;
}
.feat-card-icon img { height: 44px; width: auto; display: block; }
.feat-card-text {
    font-size: 11.5px; font-weight: 700; color: #2B3A4A;
    text-align: center; line-height: 1.75;
}

/* ── 连接教程视频 ── */
.vid-wrap {
    position: relative; background: #000; margin: 0 auto;
    aspect-ratio: 9 / 20;           /* 视频真实比例 720×1600，完整显示、不裁切 */
    width: 72%; max-width: 280px;   /* 与下方使用说明截图等宽 */
    border-radius: 24px;            /* 圆角与截图一致 */
    overflow: hidden;               /* 裁掉四角，使视频/播放按钮贴合圆角 */
}
.tut-video {
    width: 100%; height: 100%; display: block;
    object-fit: contain;        /* 不裁切（容器已是视频比例，无黑边） */
}
.vid-btn {
    position: absolute; top: 14px; right: 14px;
    width: 42px; height: 42px; border-radius: 50%;
    background: rgba(50,50,50,.52);
    backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
    border: none; cursor: pointer;
    display: flex; align-items: center; justify-content: center;
}
/* ── 下载状态：动态进度条 + 提示文字 ── */
.dl-status {
    width: 100%; box-sizing: border-box;       /* 满屏宽，灯条贴满屏幕 */
    margin: 22px 0 12px;
}
.dl-status.hidden { display: none; }
.dl-bar {                                  /* 灯条轨道：满屏宽、直角无圆角 */
    position: relative; height: 8px;
    background: #0d1320;
    overflow: hidden;
}
.dl-bar > i {                              /* 彩虹灯条：进入时 0→100% 点亮，之后彩虹持续滚动 */
    position: absolute; inset: 0; width: 0;
    background: linear-gradient(90deg,#ff0055,#ff5500,#ffcc00,#55ff00,#00ffcc,#0077ff,#aa00ff,#ff0055);
    background-size: 300% 100%;
    box-shadow: 0 0 14px rgba(80, 180, 255, .7);
    animation: led-scroll 5s linear infinite, dl-fill 1.8s cubic-bezier(.25, 1, .5, 1) forwards;
}
@keyframes led-scroll { 0% { background-position: 0% center; } 100% { background-position: 200% center; } }
@keyframes dl-fill    { from { width: 0; } to { width: 100%; } }
.dl-tip {
    margin: 14px 0 0; padding: 0 16px; font-size: 15px; line-height: 1.6;
    color: #5a6b7b; text-align: center;
}
.dl-tip a { color: #2eab6e; font-weight: 600; text-decoration: none; }
.dl-tip a:active { opacity: .7; }
.dl-ver { margin: 6px 0 0; text-align: center; font-size: 12px; color: #9aa7b8; }

/* ── 使用说明子项（全屏版） ── */
.usage-sub {
    width: 100%; padding-bottom: 40px; margin-bottom: 6px;
    border-bottom: 1px solid rgba(43,58,74,.07);
}
.usage-sub:last-child { border-bottom: none; padding-bottom: 0; }
.usage-sub-title {
    font-size: 18px; font-weight: 700; color: #2B3A4A;
    text-align: center; padding: 26px 0 20px; letter-spacing: 1px;
}
.usage-shot-full {
    width: 72%; max-width: 280px; display: block;
    margin: 0 auto 26px; border-radius: 24px;
    box-shadow: 0 6px 24px rgba(0,0,0,.18);
}
.usage-shot-full-ph {
    width: 72%; max-width: 280px; aspect-ratio: 9/18;
    display: flex; align-items: center; justify-content: center;
    margin: 0 auto 26px; border-radius: 24px;
    background: #eef4ff; border: 1px dashed #aac4e8;
    font-size: 12px; color: #88aacc;
}
.usage-desc {
    padding: 0 20px; font-size: 14px; color: #3D3D3D; line-height: 1.8;
}
.usage-desc > p { color: #4a5a7a; margin-bottom: 16px; font-size: 13px; }
.usage-btn-list { list-style: none; padding: 0; margin: 0; }
.usage-btn-item {
    display: flex; align-items: flex-start; gap: 11px; margin-bottom: 13px;
}
.ui-btn {
    flex-shrink: 0; display: flex; align-items: center; margin-top: 1px;
}
/* 图标按自身纵横比显示，统一高度，不拉伸 */
.ui-btn img { height: 30px; width: auto; display: block; }
.ui-btn svg { display: block; }
.usage-btn-text { flex: 1; font-size: 13px; color: #3D3D3D; line-height: 1.7; }