/* ===========================
   Korean Language Course — Main Stylesheet
   Based on course_template + language site index/nav additions
   =========================== */

/* ===========================
   CSS Reset
   =========================== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ===========================
   CSS Variables — Light (default)
   =========================== */
:root {
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --nav-bg: #1e293b;
    --nav-text: #f1f5f9;
    --text-color: #1e293b;
    --text-light: #64748b;
    --border-color: #e2e8f0;
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --primary-light: rgba(59, 130, 246, 0.08);
    --primary-gradient: linear-gradient(135deg, #3b82f6 0%, #6366f1 100%);
    --accent2: #e11d48;
    --code-bg: #f1f5f9;
    --code-color: #334155;
    --success-bg: #f0fdf4;
    --success-border: #22c55e;
    --warning-bg: #fffbeb;
    --warning-border: #f59e0b;
    --info-bg: #eff6ff;
    --info-border: #3b82f6;
    --danger-bg: #fef2f2;
    --danger-border: #ef4444;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.04);
    --toggle-bg: #cbd5e1;
    --table-border: #cbd5e1;
    --table-stripe: #f8fafc;
    --font-family-base: 'Segoe UI', system-ui, -apple-system, sans-serif;
    --font-family-mono: 'Cascadia Code', 'Fira Code', 'Consolas', monospace;
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
}

/* ===========================
   Dark theme
   =========================== */
[data-theme="dark"] {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --nav-bg: #0f172a;
    --nav-text: #e2e8f0;
    --text-color: #e2e8f0;
    --text-light: #94a3b8;
    --border-color: #334155;
    --primary-light: rgba(59, 130, 246, 0.15);
    --accent2: #fb7185;
    --code-bg: #1e293b;
    --code-color: #e2e8f0;
    --success-bg: rgba(34, 197, 94, 0.1);
    --warning-bg: rgba(245, 158, 11, 0.1);
    --info-bg: rgba(59, 130, 246, 0.1);
    --danger-bg: rgba(239, 68, 68, 0.1);
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.4), 0 2px 4px -2px rgba(0,0,0,0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.5), 0 4px 6px -4px rgba(0,0,0,0.3);
    --toggle-bg: #475569;
    --table-border: #475569;
    --table-stripe: #1e293b;
}

/* ===========================
   Base
   =========================== */
html { scroll-behavior: smooth; }

body {
    font-family: var(--font-family-base);
    font-size: 1rem;
    line-height: 1.7;
    color: var(--text-color);
    background: var(--bg-color);
    padding: 0;
    margin: 0;
    transition: background .3s, color .3s;
}

/* ===========================
   Site header / nav (injected by site-nav.js)
   =========================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--nav-bg);
    color: var(--nav-text);
    padding: .6rem 1.2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: .5rem;
    box-shadow: 0 2px 8px var(--shadow-sm);
}
.site-header a {
    color: var(--nav-text);
    text-decoration: none;
    font-size: .9rem;
    padding: .35rem .7rem;
    border-radius: var(--radius-sm);
    transition: background .2s;
}
.site-header a:hover { background: rgba(255,255,255,.12); }
.site-header .nav-links { display: flex; align-items: center; gap: .25rem; flex-wrap: wrap; }
.site-header .site-brand { font-weight: 700; font-size: 1.05rem; white-space: nowrap; }

/* Dark mode toggle */
.theme-toggle {
    background: var(--toggle-bg);
    border: none;
    border-radius: 999px;
    width: 52px;
    height: 28px;
    cursor: pointer;
    position: relative;
    transition: background .3s;
    flex-shrink: 0;
}
.theme-toggle::after {
    content: '';
    position: absolute;
    top: 3px; left: 3px;
    width: 22px; height: 22px;
    border-radius: 50%;
    background: #fff;
    transition: transform .3s;
    box-shadow: 0 1px 3px rgba(0,0,0,.2);
}
[data-theme="dark"] .theme-toggle { background: #3b82f6; }
[data-theme="dark"] .theme-toggle::after { transform: translateX(24px); }
.theme-toggle-label {
    display: flex; align-items: center; gap: .4rem; cursor: pointer;
    font-size: .85rem; color: var(--nav-text); user-select: none;
}
.theme-toggle-label .icon { font-size: 1rem; }

/* ===========================
   Content wrapper
   =========================== */
.content-wrap {
    max-width: 960px;
    margin: 0 auto;
    padding: 1.5rem 1.25rem 3rem;
}

/* ===========================
   Typography
   =========================== */
h1, h2, h3, h4 {
    font-weight: 700;
    line-height: 1.3;
    color: #fff;
    background: var(--primary-gradient);
    padding: .75rem 1rem;
    margin: 1.5rem 0 .75rem;
    border-radius: 8px;
}
h1 { font-size: 1.75rem; text-align: center; }
h2 { font-size: 1.35rem; }
h3 { font-size: 1.15rem; }
h4 { font-size: 1.05rem; }

p  { margin: .75rem 0; }
strong { font-weight: 700; }
a  { color: var(--primary-color); transition: color .2s; }
a:hover { text-decoration: underline; }

/* Lists */
ol, ul { margin: .5rem 0 .5rem 1.75rem; }
ol li { list-style: decimal; padding: .3rem 0; }
ul li { list-style: disc; padding: .3rem 0; }
dl { margin: .5rem 0 .5rem 1.75rem; }
dd { margin-left: 1.25rem; padding-bottom: .5rem; }

/* ===========================
   Tables
   =========================== */
.table-wrap { overflow-x: auto; }
table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem auto;
    font-size: .95rem;
}
th, td {
    border: 1px solid var(--table-border);
    padding: .55rem .75rem;
    text-align: center;
}
th { background: var(--primary-color); color: #fff; font-weight: 600; }
tr:nth-child(even) td { background: var(--table-stripe); }

/* ===========================
   Cards
   =========================== */
.card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    margin: 1rem 0;
    box-shadow: var(--shadow-sm);
    transition: box-shadow .3s, background .3s;
}
.card:hover { box-shadow: var(--shadow-md); }

.card-success { background: var(--success-bg); border-left: 4px solid var(--success-border); }
.card-warning { background: var(--warning-bg); border-left: 4px solid var(--warning-border); }
.card-info    { background: var(--info-bg);    border-left: 4px solid var(--info-border); }
.card-danger  { background: var(--danger-bg);  border-left: 4px solid var(--danger-border); }
.card-accent  { background: var(--primary-gradient); color: #fff; border: none; }
.card-accent h3, .card-accent h4, .card-accent p { color: #fff; }

/* ===========================
   Blockquote
   =========================== */
blockquote {
    margin: 1rem 0;
    padding: .85rem 1.25rem;
    background: var(--primary-light);
    border-left: 4px solid var(--primary-color);
    border-radius: 0 8px 8px 0;
    color: var(--text-color);
}

/* ===========================
   Code (minimal, for any inline code)
   =========================== */
code {
    font-family: var(--font-family-mono);
    background: var(--code-bg);
    color: var(--code-color);
    padding: .15rem .35rem;
    border-radius: 4px;
    font-size: .9em;
}

/* ===========================
   Images & SVG
   =========================== */
img { max-width: 100%; height: auto; border-radius: var(--radius-sm); }
svg { display: block; margin: 1rem auto; max-width: 100%; }

/* ===========================
   Tip / Info boxes
   =========================== */
.tip-box, .info-box, .warning-box {
    margin: 1rem 0;
    padding: 1rem 1.25rem;
    border-radius: 8px;
    border-left: 4px solid var(--accent2);
    background: var(--card-bg);
    box-shadow: 0 1px 4px var(--shadow-sm);
}
.tip-box h3, .info-box h3, .warning-box h3 {
    background: transparent;
    color: var(--accent2);
    padding: 0;
    margin: 0 0 .4rem;
    font-size: 1.05rem;
}

/* ===========================
   Quiz
   =========================== */
.quiz-container { padding: 1rem; }
.quiz-option {
    display: block;
    width: 100%;
    text-align: left;
    padding: .6rem 1rem;
    margin: .5rem 0;
    background: var(--card-bg);
    color: var(--text-color);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: .95rem;
    transition: border-color .2s, background .2s;
}
.quiz-option:hover { border-color: var(--primary-color); background: var(--primary-light); }
.quiz-option.correct { border-color: var(--success-border); background: var(--success-bg); }
.quiz-option.incorrect { border-color: var(--danger-border); background: var(--danger-bg); }
.quiz-feedback { padding: .5rem 1rem; margin-top: .5rem; border-radius: var(--radius-sm); font-weight: 500; }
.quiz-feedback.correct { color: var(--success-border); }
.quiz-feedback.incorrect { color: var(--danger-border); }

/* ===========================
   Prev / Next nav
   =========================== */
.lesson-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    margin: 2.5rem 0 1rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
    flex-wrap: wrap;
}
.lesson-nav a {
    display: inline-flex;
    align-items: center;
    gap: .35rem;
    padding: .6rem 1rem;
    background: var(--primary-color);
    color: #fff;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    font-size: .9rem;
    transition: background .2s, transform .15s;
}
.lesson-nav a:hover { background: var(--accent2); transform: translateY(-1px); }
.lesson-nav .spacer { flex: 1; }

/* Home-link: outlined "ghost" variant to distinguish from prev/next */
.lesson-nav .home-link {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}
.lesson-nav .home-link:hover {
    background: var(--primary-color);
    color: #fff;
    transform: translateY(-1px);
}

/* First lesson uses <span></span> as a prev placeholder — keep it inert */
.lesson-nav > span:empty { flex: 0 0 auto; }

/* ===========================
   Footer
   =========================== */
.site-footer {
    text-align: center;
    padding: 1.5rem 1rem;
    font-size: .85rem;
    color: var(--text-light);
    border-top: 1px solid var(--border-color);
    margin-top: 2rem;
}
.site-footer a { color: var(--primary-color); }
.site-footer p { margin: .35rem 0; }

.footer-links {
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    margin-top: .5rem;
}
.site-footer .footer-links a { text-decoration: none; }
.site-footer .footer-links a:hover { text-decoration: underline; }

/* ===========================
   INDEX PAGE — hero, card grid, progress
   =========================== */
.index-hero {
    text-align: center;
    padding: 2rem 1rem;
}
.index-hero h1 {
    background: linear-gradient(135deg, var(--primary-color), var(--accent2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-size: clamp(1.75rem, 5vw, 2.75rem);
    padding: 0;
    margin-bottom: .25rem;
}
.index-hero .subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
}

.intro-section {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 1.75rem;
    margin-bottom: 2rem;
    text-align: center;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}
.intro-section h2 { background: transparent; color: var(--primary-color); padding: 0; margin: 0 0 .75rem; }

.progress-tracker {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 1.5rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}
.progress-tracker h3 { background: transparent; color: var(--primary-color); padding: 0; margin: 0 0 .5rem; font-size: 1.15rem; }

.progress-bar {
    width: 100%;
    height: 26px;
    background: var(--border-color);
    border-radius: 13px;
    overflow: hidden;
    margin: .75rem 0;
}
.progress-fill {
    height: 100%;
    background: linear-gradient(to right, var(--primary-color), var(--accent2));
    width: 0%;
    transition: width .5s;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-weight: 700;
    font-size: .8rem;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.25rem;
    margin-bottom: 2rem;
}

.lesson-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem;
    text-decoration: none;
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    gap: .4rem;
    transition: transform .2s, box-shadow .2s, border-color .2s;
    box-shadow: var(--shadow-sm);
}
.lesson-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 6px 20px var(--shadow-sm);
    border-color: var(--primary-color);
}

.lesson-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px; height: 36px;
    border-radius: 50%;
    background: var(--accent2);
    color: #fff;
    font-weight: 700;
    font-size: .9rem;
    flex-shrink: 0;
}

.lesson-title { font-size: 1.1rem; font-weight: 700; color: var(--text-color); }
.lesson-description { font-size: .9rem; color: var(--text-light); }
.lesson-topics { font-size: .8rem; color: var(--text-light); }

/* Special lesson card (accent) */
.lesson-card.special-lesson {
    background: linear-gradient(135deg, #667eea, #764ba2);
    border-color: transparent;
    color: #fff;
}
.lesson-card.special-lesson .lesson-number { background: #fff; color: #667eea; }
.lesson-card.special-lesson .lesson-title,
.lesson-card.special-lesson .lesson-description,
.lesson-card.special-lesson .lesson-topics { color: #fff; }

/* ===========================
   Details / collapsible
   =========================== */
details { margin: .75rem 0; }
details summary {
    cursor: pointer;
    font-weight: 600;
    padding: .5rem;
    border-radius: var(--radius-sm);
    transition: background .2s;
}
details summary:hover { background: var(--primary-light); }
details[open] > summary { margin-bottom: .5rem; }

/* ===========================
   Responsive
   =========================== */
@media (max-width: 600px) {
    .site-header { padding: .5rem .75rem; }
    .site-header .site-brand { font-size: .9rem; }
    .content-wrap { padding: 1rem .75rem 2rem; }
    h1 { font-size: 1.4rem; }
    h2 { font-size: 1.15rem; }
    .course-grid { grid-template-columns: 1fr; }
    .lesson-nav { flex-direction: column; align-items: stretch; text-align: center; }
    .lesson-nav a { justify-content: center; }
    table { font-size: .85rem; }
    th, td { padding: .4rem; }
}

/* ===========================
   Print
   =========================== */
@media print {
    body { background: #fff; color: #000; }
    .site-header, .lesson-nav, .site-footer, .theme-toggle-label { display: none !important; }
    h1, h2, h3, h4 { background: none !important; color: #000 !important; }
    a { color: #000; text-decoration: underline; }
    .card { box-shadow: none; border: 1px solid #ccc; }
}

/* ===========================
   Accessibility
   =========================== */
@media (prefers-reduced-motion: reduce) {
    * { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}