:root {
    --bg: #f7faf8;
    --surface: #ffffff;
    --surface-soft: #eef7f2;
    --text: #14211c;
    --muted: #607168;
    --line: #dce8e1;
    --primary: #0f8a5f;
    --primary-dark: #086443;
    --accent: #f2b84b;
    --ink: #10231b;
    --shadow: 0 18px 45px rgba(20, 33, 28, 0.1);
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
    font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    line-height: 1.6;
}

a {
    color: inherit;
    text-decoration: none;
}

.container {
    width: min(1120px, calc(100% - 32px));
    margin: 0 auto;
}

.section {
    padding: 88px 0;
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 20;
    background: rgba(247, 250, 248, 0.92);
    border-bottom: 1px solid rgba(220, 232, 225, 0.8);
    backdrop-filter: blur(18px);
}

.header-inner {
    display: flex;
    min-height: 76px;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 800;
}

.brand-mark {
    display: grid;
    width: 38px;
    height: 38px;
    place-items: center;
    border-radius: 10px;
    background: var(--primary);
    color: #ffffff;
}

.brand-name {
    font-size: 1.25rem;
}

.primary-nav {
    display: flex;
    align-items: center;
    gap: 26px;
    color: var(--muted);
    font-size: 0.95rem;
    font-weight: 600;
}

.primary-nav a:hover,
.text-link:hover,
.footer-grid a:hover,
.footer-bottom a:hover {
    color: var(--primary);
}

.header-actions,
.hero-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.student-account-summary {
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 700;
}

.student-account-summary span + span {
    padding-left: 10px;
    border-left: 1px solid var(--line);
}

.mobile-student-account {
    display: none;
}

.header-actions form,
.mobile-student-account form {
    margin: 0;
}

.header-actions button,
.mobile-student-account button {
    font: inherit;
    cursor: pointer;
}

.btn {
    display: inline-flex;
    min-height: 42px;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    padding: 0 18px;
    border: 1px solid transparent;
    font-weight: 700;
    transition: transform 180ms ease, background 180ms ease, border-color 180ms ease;
}

.btn:hover {
    transform: translateY(-1px);
}

.btn-primary {
    background: var(--primary);
    color: #ffffff;
}

.btn-primary:hover {
    background: var(--primary-dark);
}

.btn-secondary {
    background: #ffffff;
    color: var(--ink);
    border-color: var(--line);
}

.btn-ghost {
    color: var(--primary-dark);
    border-color: var(--line);
}

.btn-large {
    min-height: 50px;
    padding: 0 24px;
}

.menu-toggle {
    display: none;
    width: 42px;
    height: 42px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    padding: 9px;
}

.menu-toggle span {
    display: block;
    height: 2px;
    margin: 5px 0;
    background: var(--ink);
}

.hero {
    min-height: calc(100vh - 76px);
    display: flex;
    align-items: center;
    padding: 70px 0 96px;
}

.hero-grid {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(320px, 0.9fr);
    align-items: center;
    gap: 64px;
}

.eyebrow {
    margin: 0 0 12px;
    color: var(--primary-dark);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0;
    text-transform: uppercase;
}

h1,
h2,
h3,
p {
    overflow-wrap: anywhere;
}

h1 {
    max-width: 720px;
    margin: 0;
    color: var(--ink);
    font-size: clamp(2.6rem, 6vw, 5.6rem);
    line-height: 0.96;
    letter-spacing: 0;
}

h2 {
    margin: 0;
    color: var(--ink);
    font-size: clamp(1.9rem, 3.5vw, 3rem);
    line-height: 1.1;
    letter-spacing: 0;
}

h3 {
    margin: 0;
    color: var(--ink);
    font-size: 1.05rem;
    line-height: 1.3;
}

.hero-copy {
    max-width: 620px;
    margin: 24px 0 32px;
    color: var(--muted);
    font-size: 1.12rem;
}

.hero-illustration {
    position: relative;
    min-height: 470px;
}

.learning-panel {
    position: absolute;
    inset: 54px 18px 36px 22px;
    border: 1px solid rgba(15, 138, 95, 0.18);
    border-radius: 18px;
    background: linear-gradient(145deg, #ffffff 0%, #eef7f2 100%);
    box-shadow: var(--shadow);
    padding: 24px;
}

.panel-top {
    display: flex;
    gap: 8px;
    margin-bottom: 32px;
}

.panel-top span {
    width: 11px;
    height: 11px;
    border-radius: 50%;
    background: var(--accent);
}

.graph-area {
    display: grid;
    height: 190px;
    grid-template-columns: repeat(4, 1fr);
    align-items: end;
    gap: 16px;
    border-bottom: 2px solid var(--line);
}

.bar {
    display: block;
    border-radius: 10px 10px 0 0;
    background: var(--primary);
}

.bar-one { height: 46%; }
.bar-two { height: 72%; background: var(--accent); }
.bar-three { height: 58%; }
.bar-four { height: 88%; background: #274c77; }

.equation-line {
    width: 80%;
    height: 12px;
    margin-top: 28px;
    border-radius: 999px;
    background: var(--line);
}

.equation-line.short {
    width: 52%;
    margin-top: 14px;
}

.formula-card {
    position: absolute;
    z-index: 2;
    border-radius: 14px;
    background: #ffffff;
    padding: 14px 18px;
    color: var(--primary-dark);
    font-weight: 800;
    box-shadow: var(--shadow);
}

.card-one {
    top: 8px;
    left: 0;
}

.card-two {
    right: 0;
    bottom: 4px;
    color: #274c77;
}

.section-heading {
    max-width: 760px;
    margin-bottom: 36px;
}

.split-heading {
    display: flex;
    max-width: none;
    align-items: end;
    justify-content: space-between;
    gap: 24px;
}

.text-link {
    color: var(--primary-dark);
    font-weight: 800;
}

.card-grid,
.article-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 20px;
}

.info-card,
.course-card,
.article-card {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface);
    box-shadow: 0 10px 24px rgba(20, 33, 28, 0.06);
}

.info-card {
    padding: 24px;
}

.info-card p,
.course-card p,
.article-card p,
.cta p,
.footer-brand p {
    margin: 10px 0 0;
    color: var(--muted);
}

.icon-badge {
    display: grid;
    width: 44px;
    height: 44px;
    place-items: center;
    margin-bottom: 18px;
    border-radius: 8px;
    background: var(--surface-soft);
    color: var(--primary-dark);
    font-weight: 900;
}

.courses {
    background: #ffffff;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(5, minmax(0, 1fr));
    gap: 18px;
}

.course-card {
    display: flex;
    min-height: 250px;
    flex-direction: column;
    justify-content: space-between;
    padding: 18px;
}

.course-thumb {
    display: grid;
    width: 58px;
    height: 58px;
    place-items: center;
    border-radius: 12px;
    background: #274c77;
    color: #ffffff;
    font-size: 1.4rem;
    font-weight: 900;
}

.course-card a,
.article-card a {
    color: var(--primary-dark);
    font-weight: 800;
}

.questions {
    background: #ffffff;
}

.question-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
}

.question-card {
    display: flex;
    min-height: 320px;
    flex-direction: column;
    justify-content: space-between;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface);
    padding: 22px;
    box-shadow: 0 10px 24px rgba(20, 33, 28, 0.06);
}

.question-card h3 {
    margin: 14px 0;
    font-size: 1.08rem;
}

.question-meta,
.question-detail-row {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.question-meta span,
.question-detail-row span,
.true-false-answer {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface-soft);
    padding: 6px 10px;
    color: var(--primary-dark);
    font-size: 0.8rem;
    font-weight: 800;
}

.question-detail-row {
    margin-bottom: 16px;
}

.question-options {
    display: grid;
    gap: 8px;
    margin: 0;
    padding-left: 20px;
}

.question-options li {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    padding: 8px 10px;
    color: var(--muted);
    font-weight: 700;
}

.question-options li.is-correct,
.true-false-answer {
    border-color: rgba(15, 138, 95, 0.32);
    background: #eef7f2;
    color: var(--primary-dark);
}

.quiz-page {
    min-height: calc(100vh - 76px);
    background: #ffffff;
}

.quiz-shell {
    width: min(100%, 980px);
    margin: 0 auto;
}

.quiz-panel {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface);
    padding: 28px;
    box-shadow: var(--shadow);
}

.quiz-selector-grid,
.quiz-topbar,
.quiz-stats,
.quiz-score,
.quiz-actions {
    display: flex;
    gap: 14px;
}

.quiz-selector-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    margin: 24px 0;
}

.quiz-selector-grid label {
    display: grid;
    gap: 8px;
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 800;
}

.quiz-selector-grid select {
    width: 100%;
    min-height: 46px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    padding: 0 12px;
    color: var(--text);
    font: inherit;
}

.quiz-topbar {
    align-items: flex-start;
    justify-content: space-between;
}

.quiz-topbar h1,
.quiz-finish h1 {
    margin: 0;
    font-size: clamp(1.7rem, 3vw, 2.5rem);
}

.quiz-score,
.quiz-stats {
    flex-wrap: wrap;
}

.quiz-score {
    justify-content: flex-end;
    min-width: 240px;
}

.quiz-score span,
.quiz-stats span,
.quiz-message,
.answer-feedback {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface-soft);
    padding: 8px 11px;
    color: var(--primary-dark);
    font-size: 0.86rem;
    font-weight: 800;
}

.quiz-message {
    margin: 18px 0;
    border-color: rgba(242, 184, 75, 0.52);
    background: #fff8e8;
    color: #735312;
}

.quiz-options {
    display: grid;
    gap: 12px;
    margin: 26px 0;
}

.quiz-option {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    padding: 14px;
    color: var(--text);
    font-weight: 700;
}

.quiz-option input {
    margin-top: 5px;
}

.quiz-fill-answer {
    display: grid;
    gap: 8px;
    color: var(--muted);
    font-weight: 800;
}

.quiz-fill-answer input {
    min-height: 48px;
    border: 1px solid var(--line);
    border-radius: 8px;
    padding: 0 12px;
    color: var(--text);
    font: inherit;
}

.quiz-option.is-correct,
.answer-feedback.is-correct {
    border-color: rgba(15, 138, 95, 0.38);
    background: #eef7f2;
    color: var(--primary-dark);
}

.quiz-option.is-wrong,
.answer-feedback.is-wrong {
    border-color: rgba(196, 72, 72, 0.32);
    background: #fff1f1;
    color: #8f2e2e;
}

.answer-feedback {
    display: grid;
    gap: 4px;
    margin-bottom: 16px;
}

.quiz-explanation {
    border-left: 4px solid var(--accent);
    background: #fffdf8;
    padding: 14px 16px;
    color: var(--muted);
}

.quiz-explanation p {
    margin: 0;
}

.quiz-actions {
    flex-wrap: wrap;
    margin-top: 24px;
}

.why-card {
    border-top: 4px solid var(--accent);
}

.article-card {
    overflow: hidden;
}

.article-image {
    height: 150px;
    background:
        linear-gradient(135deg, rgba(15, 138, 95, 0.78), rgba(39, 76, 119, 0.82)),
        repeating-linear-gradient(45deg, transparent 0 12px, rgba(255, 255, 255, 0.26) 12px 14px);
}

.article-thumb {
    display: block;
    width: 100%;
    height: 190px;
    object-fit: cover;
}

.article-content {
    padding: 22px;
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 12px;
    margin-bottom: 10px;
}

.article-meta span {
    display: inline-block;
    color: var(--primary-dark);
    font-size: 0.8rem;
    font-weight: 800;
}

.cta {
    padding-top: 40px;
}

.blog-hero {
    padding: 76px 0 48px;
}

.blog-hero h1,
.post-header h1 {
    font-size: clamp(2.3rem, 5vw, 4.6rem);
}

.blog-listing {
    padding-top: 28px;
}

.pagination-wrap {
    margin-top: 34px;
}

.empty-state {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface);
    padding: 36px;
}

.empty-state p {
    margin: 10px 0 0;
    color: var(--muted);
}

.narrow-container {
    max-width: 860px;
}

.post-header {
    margin-top: 28px;
}

.post-byline,
.post-excerpt {
    color: var(--muted);
}

.post-byline {
    margin: 18px 0 0;
    font-weight: 700;
}

.post-featured-image {
    display: block;
    width: 100%;
    max-height: 460px;
    margin: 34px 0;
    border-radius: 8px;
    object-fit: cover;
}

.post-excerpt {
    margin: 0 0 28px;
    font-size: 1.18rem;
    font-weight: 600;
}

.post-content {
    color: var(--text);
    font-size: 1.04rem;
}

.post-content h2,
.post-content h3 {
    margin: 34px 0 12px;
}

.post-content p,
.post-content ul,
.post-content ol {
    margin: 0 0 18px;
}

.post-content a {
    color: var(--primary-dark);
    font-weight: 700;
}

.post-content img {
    max-width: 100%;
    border-radius: 8px;
}

.tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 34px;
    padding-top: 24px;
    border-top: 1px solid var(--line);
}

.tag-list span {
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    padding: 7px 11px;
    color: var(--primary-dark);
    font-size: 0.86rem;
    font-weight: 800;
}

.cta-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 32px;
    border-radius: 8px;
    background: var(--ink);
    padding: 42px;
    color: #ffffff;
}

.cta h2,
.cta .eyebrow {
    color: #ffffff;
}

.cta p {
    max-width: 680px;
    color: rgba(255, 255, 255, 0.74);
}

.site-footer {
    background: #ffffff;
    border-top: 1px solid var(--line);
    padding: 54px 0 24px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.4fr repeat(3, 1fr);
    gap: 34px;
}

.footer-grid h2 {
    margin-bottom: 14px;
    font-size: 1rem;
}

.footer-grid ul {
    display: grid;
    gap: 8px;
    margin: 0;
    padding: 0;
    color: var(--muted);
    list-style: none;
}

.social-links {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.social-links a {
    display: grid;
    width: 38px;
    height: 38px;
    place-items: center;
    border: 1px solid var(--line);
    border-radius: 8px;
    color: var(--primary-dark);
    font-weight: 800;
}

.footer-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    margin-top: 42px;
    padding-top: 20px;
    border-top: 1px solid var(--line);
    color: var(--muted);
    font-size: 0.92rem;
}

.footer-bottom p {
    margin: 0;
}

.footer-bottom div {
    display: flex;
    gap: 18px;
}

@media (max-width: 980px) {
    .header-actions {
        display: none;
    }

    .mobile-student-account {
        display: block;
        padding: 14px 16px;
    }

    .mobile-student-account .student-account-summary {
        align-items: flex-start;
        flex-direction: column;
        gap: 4px;
        margin-bottom: 12px;
    }

    .mobile-student-account .student-account-summary span + span {
        padding-left: 0;
        border-left: 0;
    }

    .mobile-student-account .btn {
        width: 100%;
    }

    .menu-toggle {
        display: block;
    }

    .primary-nav {
        position: absolute;
        top: 76px;
        right: 16px;
        left: 16px;
        display: none;
        flex-direction: column;
        align-items: stretch;
        gap: 0;
        border: 1px solid var(--line);
        border-radius: 8px;
        background: #ffffff;
        box-shadow: var(--shadow);
        overflow: hidden;
    }

    .primary-nav.is-open {
        display: flex;
    }

    .primary-nav a {
        padding: 14px 16px;
        border-bottom: 1px solid var(--line);
    }

    .primary-nav a:last-child {
        border-bottom: 0;
    }

    .hero-grid,
    .quiz-topbar,
    .footer-grid {
        grid-template-columns: 1fr;
        flex-direction: column;
    }

    .hero {
        min-height: auto;
    }

    .course-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .quiz-selector-grid {
        grid-template-columns: 1fr;
    }

    .card-grid,
    .article-grid,
    .question-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (max-width: 640px) {
    .container {
        width: min(100% - 24px, 1120px);
    }

    .section {
        padding: 62px 0;
    }

    .hero {
        padding: 48px 0 68px;
    }

    .hero-grid {
        gap: 34px;
    }

    .hero-actions,
    .split-heading,
    .cta-inner,
    .footer-bottom {
        align-items: stretch;
        flex-direction: column;
    }

    .hero-actions .btn,
    .cta .btn {
        width: 100%;
    }

    .hero-illustration {
        min-height: 360px;
    }

    .learning-panel {
        inset: 34px 8px 30px;
        padding: 18px;
    }

    .card-grid,
    .article-grid,
    .course-grid,
    .question-grid {
        grid-template-columns: 1fr;
    }

    .course-card {
        min-height: 220px;
    }

    .question-card {
        min-height: 0;
    }

    .quiz-panel {
        padding: 20px;
    }

    .quiz-score {
        min-width: 0;
        justify-content: flex-start;
    }

    .cta-inner {
        padding: 28px;
    }

    .footer-bottom div {
        flex-direction: column;
        gap: 8px;
    }
}