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

:root {
    --color-bg: #fafafa;
    --color-text: #1a1a1a;
    --color-muted: #6b6b6b;
    --color-border: #e5e5e5;
    --color-button: #9a9a9a;
    --color-button-hover: #e67e22;
    --color-active: #e67e22;
    --font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    --max-width: 720px;
}

body {
    font-family: var(--font-family);
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    border-bottom: 1px solid var(--color-border);
    background: #fff;
}

.nav {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 1.25rem 1.5rem;
    display: flex;
    gap: 2rem;
    justify-content: center;
}

.nav__link {
    color: var(--color-muted);
    text-decoration: none;
    font-size: 0.95rem;
    letter-spacing: 0.02em;
    transition: color 0.2s ease;
}

.nav__link:hover,
.nav__link--active {
    color: var(--color-active);
}

/* Main */
.main {
    flex: 1;
    max-width: var(--max-width);
    width: 100%;
    margin: 0 auto;
    padding: 3rem 1.5rem;
}

.page__intro {
    font-size: 1.1rem;
    color: var(--color-text);
    margin-bottom: 2rem;
    text-align: center;
}

.page__body {
    font-size: 0.95rem;
    color: var(--color-muted);
    line-height: 1.7;
    text-align: center;
    max-width: 560px;
    margin: 0 auto;
}

.page__body p + p {
    margin-top: 1rem;
}

.page__empty {
    text-align: center;
    color: var(--color-muted);
    font-size: 0.95rem;
}

/* Course list */
.course-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 560px;
    margin: 0 auto;
}

.course-list__item {
    padding: 1.25rem 1.5rem;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: 4px;
}

.course-list__title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 0.5rem;
}

.course-list__desc {
    font-size: 0.9rem;
    color: var(--color-muted);
    line-height: 1.6;
}

/* Document buttons */
.doc-buttons {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 400px;
    margin: 0 auto;
}

.doc-button {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    min-height: 52px;
    padding: 0.875rem 1.25rem;
    background: var(--color-button);
    color: #fff;
    text-decoration: none;
    font-size: 0.95rem;
    text-align: center;
    line-height: 1.3;
    border-radius: 4px;
    border: none;
    cursor: pointer;
    transition: background 0.2s ease;
    -webkit-tap-highlight-color: transparent;
}

.doc-button:hover {
    background: var(--color-button-hover);
}

.doc-button--disabled {
    opacity: 0.55;
    cursor: not-allowed;
    pointer-events: none;
}

/* Footer */
.footer {
    border-top: 1px solid var(--color-border);
    background: #fff;
    padding: 1.25rem 1.5rem;
    text-align: center;
}

.footer p {
    font-size: 0.85rem;
    color: var(--color-muted);
}

/* Mobile */
@media (max-width: 480px) {
    .nav {
        gap: 1rem;
        padding: 1rem 0.75rem;
        flex-wrap: wrap;
    }

    .nav__link {
        font-size: 0.875rem;
        padding: 0.25rem 0;
    }

    .main {
        padding: 2rem 1rem;
    }

    .page__intro {
        font-size: 1rem;
    }

    .doc-buttons {
        max-width: 100%;
    }

    .doc-button {
        min-height: 48px;
        font-size: 0.9rem;
        padding: 0.75rem 1rem;
    }

    .course-list__item {
        padding: 1rem 1.25rem;
    }
}