* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    background-color: #020706;
    color: #e9fff2;
    font-family: "Be Vietnam Pro", Arial, sans-serif;
    line-height: 1.65;
}

/* HEADER */

.header {
    height: 82px;
    padding: 0 56px;
    display: flex;
    justify-content: space-between;
    align-items: center;

    background-color: rgba(2, 7, 6, 0.92);
    border-bottom: 1px solid rgba(0, 255, 170, 0.16);

    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(12px);
}

.brand {
    display: flex;
    align-items: center;
    gap: 14px;
}

.brand img {
    width: 42px;
    height: 42px;
    object-fit: contain;
    border-radius: 10px;
}

.brand span {
    font-family: "Noto Serif", Georgia, serif;
    font-size: 23px;
    font-weight: 800;
    font-style: italic;
    color: #eafff4;
}

.nav {
    display: flex;
    gap: 30px;
}

.nav a {
    text-decoration: none;
    color: #9bb7aa;
    font-size: 14px;
    letter-spacing: 1.2px;
}

.nav a:hover {
    color: #28f7a4;
}

/* HERO */

.hero {
    min-height: calc(100vh - 82px);
    padding: 110px 10% 90px 12%;
    display: grid;
    grid-template-columns: 1.25fr 0.85fr;
    gap: 70px;
    align-items: center;

    background:
        radial-gradient(circle at 80% 30%, rgba(18, 185, 255, 0.18), transparent 32%),
        radial-gradient(circle at 70% 70%, rgba(72, 255, 113, 0.15), transparent 32%),
        linear-gradient(135deg, #020706 0%, #05130f 55%, #020706 100%);
}

.small-title,
.section-label {
    font-size: 14px;
    font-weight: 600;
    letter-spacing: 4px;
    text-transform: uppercase;
    color: #28f7a4;
    margin-bottom: 24px;
}

h1 {
    font-family: "Noto Serif", Georgia, serif;
    font-size: 76px;
    line-height: 1.04;
    font-weight: 800;
    letter-spacing: -1.5px;
    color: #f1fff7;
    margin-bottom: 34px;
}

h1 span {
    display: block;
    color: #28f7a4;
    font-style: italic;
    font-size: 52px;
    line-height: 1.15;
    margin-top: 8px;
}

.description {
    max-width: 780px;
    font-size: 21px;
    line-height: 1.9;
    color: #a9beb5;
    margin-bottom: 42px;
}

.hero-actions {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.btn {
    display: inline-block;
    padding: 14px 24px;
    border-radius: 999px;
    text-decoration: none;
    font-size: 15px;
    font-weight: 700;
    transition: 0.2s ease;
}

.btn.primary {
    background: linear-gradient(90deg, #0da7ff, #28f7a4);
    color: #00110a;
}

.btn.primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 30px rgba(40, 247, 164, 0.22);
}

.btn.secondary {
    border: 1px solid rgba(40, 247, 164, 0.45);
    color: #28f7a4;
}

.btn.secondary:hover {
    background-color: rgba(40, 247, 164, 0.08);
}

/* LOGO CARD */

.hero-logo-card {
    display: flex;
    justify-content: center;
    align-items: center;

    padding: 34px;
    border-radius: 30px;

    background:
        radial-gradient(circle at center, rgba(40, 247, 164, 0.13), transparent 55%),
        rgba(255, 255, 255, 0.035);

    border: 1px solid rgba(40, 247, 164, 0.16);
    box-shadow: 0 30px 80px rgba(0, 255, 170, 0.08);
}

.hero-logo-card img {
    width: 100%;
    max-width: 420px;
    object-fit: contain;
}

/* SECTIONS */

.section {
    padding: 100px 10%;
    background-color: #020706;
    border-top: 1px solid rgba(0, 255, 170, 0.12);
}

.dark-section {
    background:
        radial-gradient(circle at 20% 20%, rgba(13, 167, 255, 0.10), transparent 30%),
        radial-gradient(circle at 80% 70%, rgba(40, 247, 164, 0.08), transparent 30%),
        #04100d;
}

.section h2 {
    font-family: "Noto Serif", Georgia, serif;
    font-size: 52px;
    line-height: 1.15;
    color: #f1fff7;
    margin-bottom: 34px;
}

.section h2 span,
.section em {
    color: #28f7a4;
    font-style: italic;
}

.section p {
    font-size: 18px;
    line-height: 1.9;
    color: #a9beb5;
}

.section-intro {
    max-width: 900px;
    margin-bottom: 40px;
}

/* GENERAL LAYOUT */

.two-columns {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 52px;
}

.cards {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 26px;
}

/* TEAM */

.team-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 26px;
    margin-top: 60px;
}

.team-card {
    background: rgba(255, 255, 255, 0.045);
    border: 1px solid rgba(40, 247, 164, 0.16);
    border-radius: 22px;
    padding: 30px;
}

.team-avatar {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background: linear-gradient(90deg, #0da7ff, #28f7a4);
    color: #00110a;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 800;
    margin-bottom: 22px;
}

.team-card h3 {
    font-family: "Noto Serif", Georgia, serif;
    font-size: 28px;
    color: #f1fff7;
    margin-bottom: 8px;
}

.team-role {
    color: #28f7a4 !important;
    font-size: 14px !important;
    letter-spacing: 2px;
    text-transform: uppercase;
    margin-bottom: 16px;
}

/* ACTIVITIES */

.activity-list {
    margin-top: 40px;
    display: grid;
    gap: 34px;
}

.activity-block {
    padding-left: 4px;
}

.activity-block h3 {
    color: #f1fff7;
    font-size: 26px;
    margin-bottom: 14px;
}

.activity-block p {
    margin-bottom: 8px;
}

.green-dot {
    color: #28f7a4;
    font-weight: 800;
    margin-right: 10px;
}

/* COURSE */

.course-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 26px;
}

.two-course-grid {
    grid-template-columns: repeat(2, 1fr);
}

.course-card {
    background: rgba(255, 255, 255, 0.045);
    border: 1px solid rgba(40, 247, 164, 0.16);
    border-radius: 22px;
    padding: 30px;
}

.course-title {
    color: #28f7a4;
    font-family: "Noto Serif", Georgia, serif;
    font-size: 38px;
    line-height: 1.2;
    font-weight: 800;
    margin-bottom: 26px;
}

.course-card ul {
    padding-left: 20px;
    color: #e9fff2;
}

.course-card li {
    margin-bottom: 10px;
    font-size: 18px;
    line-height: 1.7;
}

/* YOUTUBE PLAYLIST TIMELINE */

.playlist-timeline {
    position: relative;
    margin-top: 45px;
    padding-left: 42px;
}

.playlist-timeline::before {
    content: "";
    position: absolute;
    left: 9px;
    top: 10px;
    bottom: 10px;
    width: 2px;
    background: rgba(40, 247, 164, 0.25);
}

.playlist-item {
    position: relative;
    margin-bottom: 38px;
}

.playlist-item:last-child {
    margin-bottom: 0;
}

.playlist-dot {
    position: absolute;
    left: -42px;
    top: 8px;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    border: 2px solid #28f7a4;
    background: #04100d;
}

.playlist-item.active .playlist-dot {
    background: #28f7a4;
}

.playlist-item h3 {
    color: #28f7a4;
    font-size: 26px;
    margin-bottom: 10px;
}

.playlist-item p {
    max-width: 900px;
}

/* TABLE */

.problem-table {
    border: 1px solid rgba(40, 247, 164, 0.16);
    border-radius: 20px;
    overflow: hidden;
    background: rgba(255, 255, 255, 0.04);
}

.problem-row {
    display: grid;
    grid-template-columns: 1fr 1fr 1.5fr;
    padding: 18px 24px;
    border-bottom: 1px solid rgba(40, 247, 164, 0.12);
    color: #a9beb5;
}

.problem-row:last-child {
    border-bottom: none;
}

.problem-row.head {
    background: linear-gradient(90deg, #0da7ff, #28f7a4);
    color: #00110a;
    font-weight: 800;
}

/* CONTACT */

.contact-section {
    padding-bottom: 140px;
}

.contact-box {
    margin: 32px 0;
    padding: 30px;
    border-radius: 22px;
    background: rgba(255, 255, 255, 0.045);
    border: 1px solid rgba(40, 247, 164, 0.16);
}

.contact-box p {
    margin-bottom: 8px;
}

/* RESPONSIVE */

@media (max-width: 900px) {
    .header {
        padding: 0 24px;
    }

    .nav {
        display: none;
    }

    .hero {
        grid-template-columns: 1fr;
        padding: 70px 24px;
    }

    h1 {
        font-size: 44px;
    }

    h1 span {
        font-size: 34px;
    }

    .description {
        font-size: 17px;
    }

    .section {
        padding: 70px 24px;
    }

    .section h2 {
        font-size: 34px;
    }

    .two-columns,
    .cards,
    .team-grid,
    .course-grid,
    .two-course-grid {
        grid-template-columns: 1fr;
    }

    .problem-row {
        grid-template-columns: 1fr;
        gap: 6px;
    }
}

.contact-box a {
    color: #28f7a4;
    text-decoration: none;
    font-weight: 700;
}

.contact-box a:hover {
    text-decoration: underline;
}

.social-actions {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    margin-bottom: 20px;
}

.back-top-btn {
    margin-top: 8px;
}