.course-hero {
    position: relative;
    overflow: hidden;
    padding: 72px 0 58px;
    text-align: center;
    background:
        radial-gradient(ellipse at 50% 0, rgba(242, 106, 60, .16), transparent 58%),
        linear-gradient(180deg, #10131a, var(--bg));
}
.course-hero-inner { max-width: 1320px; }
.course-eyebrow, .course-kicker {
    color: #ffad8b;
    font-size: 12px;
    font-weight: 800;
    letter-spacing: 1.8px;
}
.course-eyebrow {
    display: inline-flex;
    padding: 7px 13px;
    border: 1px solid var(--brand-line);
    border-radius: 999px;
    background: var(--brand-bg);
}
.course-hero h1 {
    margin: 20px 0 16px;
    color: #fff;
    font-size: clamp(28px, 4vw, 52px);
    line-height: 1.1;
    letter-spacing: -1.5px;
    white-space: nowrap;
}
.course-hero p {
    max-width: 820px;
    margin: 0 auto;
    color: var(--muted);
    font-size: 17px;
}
.course-hero p strong { color: var(--soft); }
.course-hero-actions, .course-points {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    gap: 12px;
}
.course-hero-actions { margin-top: 27px; }
.course-points {
    gap: 12px 24px;
    margin-top: 25px;
    color: var(--soft);
    font-size: 14px;
    font-weight: 600;
}
.course-points span::before { content: "✓ "; color: var(--ok); font-weight: 900; }
.course-section { padding: 54px 0 72px; }
.course-section-heading { max-width: 720px; margin: 0 auto 30px; text-align: center; }
.course-section-heading h2 {
    margin: 7px 0;
    color: #fff;
    font-size: clamp(28px, 4vw, 38px);
    line-height: 1.2;
}
.course-section-heading p { margin: 0; color: var(--muted); }
.course-section-heading code {
    padding: 2px 6px;
    border: 1px solid var(--line2);
    border-radius: 5px;
    color: #ffad8b;
    background: var(--panel2);
}
.course-player {
    display: grid;
    grid-template-columns: minmax(270px, 330px) minmax(0, 1fr);
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: 20px;
    background: var(--panel);
    box-shadow: 0 22px 65px rgba(0, 0, 0, .28);
}
.course-sidebar { min-width: 0; border-right: 1px solid var(--line); background: #10131a; }
.course-sidebar-heading { padding: 20px 20px 16px; border-bottom: 1px solid var(--line); }
.course-sidebar-heading h3 { margin: 0; color: #fff; font-size: 18px; }
.course-sidebar-heading p { margin: 3px 0 0; color: var(--muted); font-size: 13px; }
.course-lesson-list { padding: 10px 0 14px; }
.course-chapter {
    margin: 0;
    padding: 12px 18px 7px;
    color: var(--brand);
    font-size: 11px;
    font-weight: 800;
    letter-spacing: 1px;
}
.course-lesson {
    display: flex;
    align-items: center;
    gap: 11px;
    padding: 12px 16px;
    color: var(--soft);
    font-size: 14px;
    line-height: 1.45;
    text-decoration: none;
    transition: background .15s, color .15s;
}
.course-lesson:hover, .course-lesson.active { color: #fff; background: rgba(242, 106, 60, .12); }
.course-lesson.active { box-shadow: inset 3px 0 var(--brand); }
.course-lesson-number {
    display: grid;
    flex: 0 0 28px;
    width: 28px;
    height: 28px;
    place-items: center;
    border: 1px solid var(--line2);
    border-radius: 50%;
    color: var(--muted);
    font-size: 12px;
    font-weight: 800;
}
.course-lesson.active .course-lesson-number {
    border-color: var(--brand);
    color: #fff;
    background: var(--brand);
}
.course-lesson > span:nth-child(2) { flex: 1; }
.course-lesson b { color: inherit; }
.course-lesson-arrow { color: var(--muted); font-size: 22px; }
.course-detail { min-width: 0; }
.course-preview {
    position: relative;
    display: grid;
    min-height: 330px;
    aspect-ratio: 16 / 8.6;
    overflow: hidden;
    place-items: center;
    background:
        linear-gradient(135deg, rgba(10, 15, 23, .1), rgba(7, 10, 16, .55)),
        radial-gradient(ellipse at 68% 32%, rgba(242, 106, 60, .65), transparent 34%),
        linear-gradient(145deg, #1d3858, #101c30 64%, #0c111b);
}
.course-youtube-player, .course-preview iframe {
    position: absolute;
    inset: 0;
    z-index: 2;
    width: 100%;
    height: 100%;
    border: 0;
}
.course-youtube-player[hidden] { display: none; }
.course-preview iframe { display: block !important; }
.course-video-cover {
    position: absolute;
    inset: 0;
    z-index: 3;
    display: grid;
    width: 100%;
    height: 100%;
    padding: 0;
    place-items: center;
    overflow: hidden;
    border: 0;
    background: #080d15;
    cursor: pointer;
}
.course-video-cover[hidden] { display: none; }
.course-video-cover img {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    opacity: .78;
}
.course-video-play {
    position: relative;
    display: grid;
    width: 76px;
    height: 54px;
    padding-left: 4px;
    place-items: center;
    border-radius: 14px;
    color: #fff;
    background: #f00;
    box-shadow: 0 8px 28px rgba(0, 0, 0, .35);
    font-size: 24px;
    transition: transform .18s ease, background .18s ease;
}
.course-video-cover:hover .course-video-play { transform: scale(1.08); background: #d90000; }
.course-preview [hidden] { display: none !important; }
.course-preview::before, .course-preview::after {
    position: absolute;
    width: 240px;
    height: 240px;
    border: 1px solid rgba(255, 255, 255, .09);
    border-radius: 50%;
    content: "";
}
.course-preview::before { transform: scale(1.45); }
.course-preview::after { transform: scale(2.1); }
.course-preview-glow {
    position: absolute;
    right: 7%;
    bottom: -42%;
    width: 52%;
    height: 85%;
    border-radius: 50%;
    background: rgba(242, 106, 60, .19);
    filter: blur(35px);
}
.course-preview-content {
    position: relative;
    z-index: 1;
    display: grid;
    justify-items: center;
    gap: 14px;
}
.course-preview-mark {
    color: rgba(255, 255, 255, .16);
    font-size: clamp(48px, 8vw, 90px);
    font-weight: 900;
    letter-spacing: -5px;
    line-height: .9;
}
.course-play-icon {
    display: grid;
    width: 60px;
    height: 60px;
    margin-top: -6px;
    padding-left: 4px;
    place-items: center;
    border: 1px solid rgba(255, 255, 255, .6);
    border-radius: 50%;
    color: var(--brand);
    background: #fff;
    box-shadow: 0 10px 35px rgba(0, 0, 0, .25);
}
.course-preview-caption, .course-preview-tag {
    color: rgba(255, 255, 255, .8);
    font-size: 10px;
    font-weight: 800;
    letter-spacing: 2px;
}
.course-preview-tag {
    position: absolute;
    right: 16px;
    bottom: 14px;
    z-index: 1;
    padding: 6px 9px;
    border: 1px solid rgba(255, 255, 255, .2);
    border-radius: 5px;
    background: rgba(0, 0, 0, .25);
    font-size: 9px;
    letter-spacing: 1px;
}
.course-detail-content { padding: 24px 28px 28px; }
.course-label { color: var(--brand); font-size: 12px; font-weight: 800; letter-spacing: .8px; }
.course-detail-content h3 { margin: 5px 0 8px; color: #fff; font-size: 26px; line-height: 1.25; }
.course-detail-content p { margin: 0 0 20px; color: var(--muted); }
.course-bottom { padding: 0 0 72px; }
.course-bottom-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 30px;
    padding: 36px;
    border: 1px solid var(--line2);
    border-radius: 20px;
    background:
        radial-gradient(ellipse at 0 0, rgba(242, 106, 60, .14), transparent 55%),
        linear-gradient(135deg, #151b26, #10131a);
}
.course-bottom-card h2 { margin: 7px 0 8px; color: #fff; font-size: clamp(24px, 3vw, 32px); line-height: 1.2; }
.course-bottom-card p { max-width: 700px; margin: 0; color: var(--muted); }
.course-bottom-actions { display: flex; flex: 0 0 auto; flex-wrap: wrap; gap: 10px; }
.course-bottom-actions .btn { white-space: nowrap; }
.course-bottom-actions .btn.zalo { border-color: #2563eb; background: #1677ff; }

@media (max-width: 900px) {
    .course-player { grid-template-columns: 1fr; }
    .course-sidebar { border-right: 0; border-bottom: 1px solid var(--line); }
    .course-lesson-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); padding-bottom: 12px; }
    .course-chapter { grid-column: 1 / -1; }
    .course-bottom-card { align-items: flex-start; flex-direction: column; }
}
@media (max-width: 700px) {
    .course-hero { padding: 48px 0 40px; }
    .course-hero h1 {
        font-size: clamp(30px, 8vw, 40px);
        letter-spacing: -.8px;
        white-space: normal;
    }
    .course-hero p { font-size: 16px; }
    .course-hero-actions { align-items: stretch; flex-direction: column; }
    .course-hero-actions .btn { width: 100%; }
    .course-points { align-items: flex-start; flex-direction: column; gap: 7px; width: fit-content; margin: 22px auto 0; }
    .course-section { padding: 42px 0 54px; }
    .course-lesson-list { display: block; }
    .course-preview {
        width: 100%;
        min-height: 0;
        aspect-ratio: 16 / 9;
    }
    .course-detail-content { padding: 20px; }
    .course-detail-content h3 { font-size: 22px; }
    .course-bottom { padding-bottom: 52px; }
    .course-bottom-card { gap: 20px; padding: 24px 20px; }
    .course-bottom-actions { width: 100%; }
    .course-bottom-actions .btn { width: 100%; }
}