.course-page {
    min-height: 100vh;
    background: var(--surface-1);
    color: var(--text-secondary);
}

.course-main {
    width: min(1100px, calc(100% - 40px));
    margin: 0 auto;
    padding: 40px 0 70px;
}

.back-link {
    display: inline-block;
    margin-bottom: 28px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 1rem;
}

.back-link:hover {
    color: var(--gold-light);
    text-decoration: underline;
}

.course-hero {
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 22px;
    padding: 36px;
    box-shadow: var(--shadow-md);
}

.course-heading {
    display: flex;
    align-items: center;
    gap: 18px;
}

.course-icon {
    display: grid;
    place-items: center;
    width: 64px;
    height: 64px;
    border-radius: 18px;
    background: var(--gold);
    color: var(--white);
    font-size: 2rem;
}

.course-level {
    margin: 0 0 6px;
    color: var(--text-muted);
    font-size: 0.9rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.course-title {
    margin: 0;
    color: var(--text-primary);
    font-size: clamp(2.4rem, 6vw, 4.5rem);
    line-height: 1;
}

.course-description {
    max-width: 760px;
    margin: 26px 0;
    color: var(--text-secondary);
    font-size: 1.1rem;
    line-height: 1.7;
}

.course-information {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 18px;
    margin-top: 28px;
}

.course-information-card {
    background: var(--surface-2);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 20px;
}

.information-label {
    margin: 0 0 8px;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.information-value {
    margin: 0;
    color: var(--text-primary);
    font-size: 1.2rem;
    font-weight: 700;
}

.course-progress-section {
    margin-top: 30px;
}

.course-progress-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
    font-weight: 700;
}

.course-progress-header p {
    margin: 0;
    color: var(--text-secondary);
}

.course-progress-bar {
    width: 100%;
    height: 12px;
    overflow: hidden;
    border-radius: 999px;
    background: var(--surface-4);
}

.course-progress-value {
    height: 100%;
    border-radius: inherit;
    background: var(--gold);
}

.chapter-section {
    margin-top: 40px;
    padding-left: 36px;
    padding-right: 36px;
    box-sizing: border-box;
}

.section-heading h2 {
    margin: 0;
    color: var(--text-primary);
    font-size: 2rem;
}

.section-heading p {
    margin: 8px 0 0;
    color: var(--text-muted);
}

.chapter-path {
    margin-top: 24px;
}

.chapter-path-track {
    position: relative;
    padding: 6px 0 14px;
}

.chapter-path-track::before {
    content: "";
    position: absolute;
    top: 10px;
    bottom: 10px;
    left: 50%;
    width: 2px;
    transform: translateX(-50%);
    background-repeat: repeat-y;
    background-image: linear-gradient(var(--border) 60%, transparent 0%);
    background-size: 2px 14px;
}

.chapter-stone-row {
    display: flex;
    position: relative;
    margin-bottom: 18px;
}

.chapter-stone-row.left {
    justify-content: flex-start;
}

.chapter-stone-row.right {
    justify-content: flex-end;
}

.course-final-section {
    margin-top: 40px;
    padding: 28px 36px;
    box-sizing: border-box;
    border: 1px solid var(--gold);
    border-radius: 18px;
    background: var(--surface-3);
}

.course-final-button {
    display: inline-block;
    margin-top: 18px;
    padding: 14px 22px;
    border: 1px solid var(--gold-light);
    border-radius: var(--radius-md);
    background: var(--gold);
    color: var(--text-primary);
    font-weight: 800;
    text-decoration: none;
}

.course-final-button:hover {
    filter: brightness(1.08);
}

.chapter-card {
    position: relative;
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: center;
    gap: 20px;
    width: 46%;
    max-width: 460px;
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 18px;
    padding: 22px;
    box-shadow: var(--shadow-sm);
    transition:
        transform var(--transition),
        border-color var(--transition),
        box-shadow var(--transition);
}

.chapter-card:hover {
    transform: translateY(-3px);
    border-color: var(--gold-light);
    box-shadow: var(--shadow-md);
}

.chapter-card.complete {
    border-color: var(--success);
}

.chapter-card.active {
    border-color: var(--gold-light);
    box-shadow: 0 0 0 3px color-mix(in srgb, var(--gold) 18%, transparent);
}

.chapter-number {
    display: grid;
    place-items: center;
    width: 44px;
    height: 44px;
    flex-shrink: 0;
    border-radius: 50%;
    background: var(--gold);
    color: var(--white);
    font-weight: 800;
    border: 3px solid var(--surface-1);
}

.chapter-stone-row.left .chapter-card .chapter-number {
    position: absolute;
    right: -22px;
    top: 50%;
    transform: translateY(-50%);
}

.chapter-stone-row.right .chapter-card .chapter-number {
    position: absolute;
    left: -22px;
    top: 50%;
    transform: translateY(-50%);
}

.chapter-card.complete .chapter-number {
    background: var(--success);
}

.chapter-card.active .chapter-number {
    background: var(--gold-light);
}

.chapter-details h3 {
    margin: 0 0 6px;
    color: var(--text-primary);
}

.chapter-details p {
    margin: 0;
    color: var(--text-muted);
}

.chapter-button {
    border: 1px solid var(--gold);
    border-radius: 12px;
    padding: 12px 18px;
    background: var(--gold);
    color: var(--white);
    font-weight: 700;
    cursor: pointer;
    transition:
        background var(--transition),
        border-color var(--transition),
        transform var(--transition-fast),
        box-shadow var(--transition);
}

.chapter-button:hover {
    background: var(--gold-light);
    border-color: var(--gold-light);
    transform: translateY(-2px);
    box-shadow: 0 10px 22px rgba(78, 143, 255, 0.25);
}

.no-chapters,
.course-error {
    background: var(--surface-3);
    border: 1px solid var(--border);
    border-radius: 18px;
    padding: 28px;
    color: var(--text-secondary);
}

.no-chapters h3,
.course-error h1 {
    margin-top: 0;
    color: var(--text-primary);
}

/* ===========================
   Back Button
=========================== */

.course-topbar {
    display: flex;
    align-items: center;
    min-height: 72px;
    margin-left: 90px;
    margin-bottom: 24px;
}

.back-button {
    display: inline-flex;
    align-items: center;
    padding: 10px 18px;
    border: 2px solid var(--border);
    border-radius: 14px;
    background: var(--surface-3);
    color: var(--text-primary);
    font-weight: 700;
    text-decoration: none;
    transition:
        background var(--transition),
        border-color var(--transition),
        color var(--transition),
        transform var(--transition-fast);
}

.back-button:hover {
    background: var(--gold);
    border-color: var(--gold);
    color: var(--white);
    transform: translateY(-2px);
}

@media (max-width: 760px) {
    .course-main {
        width: min(100% - 24px, 1100px);
        padding-top: 24px;
    }

    .course-hero {
        padding: 24px;
    }

    .course-information {
        grid-template-columns: 1fr;
    }

    .chapter-path-track::before {
        left: 20px;
    }

    .chapter-stone-row.left,
    .chapter-stone-row.right {
        justify-content: center;
        padding-left: 40px;
    }

    .chapter-card {
        grid-template-columns: 1fr;
        width: 100%;
        max-width: none;
    }

    .chapter-stone-row.left .chapter-card .chapter-number,
    .chapter-stone-row.right .chapter-card .chapter-number {
        left: -40px;
        right: auto;
        top: 22px;
        transform: none;
    }

    .chapter-button {
        grid-column: 1 / -1;
        width: 100%;
    }

    .chapter-section {
        padding-left: 20px;
        padding-right: 20px;
    }
}