/* =============================================================
   Certia Elite Learning - Maths Platform - Main Stylesheet
   ============================================================= */

:root {
    --primary: #1a3a6b;
    --primary-dark: #12294d;
    --accent: #2f80ed;
    --accent-light: #eaf2fd;
    --success: #1e8e5a;
    --warning: #c07f13;
    --danger: #c0392b;
    --bg: #f5f7fb;
    --card: #ffffff;
    --text: #1c2430;
    --muted: #64748b;
    --border: #dbe3ee;
    --radius: 10px;
    --shadow: 0 2px 10px rgba(18, 41, 77, 0.08);
    --font: "Segoe UI", system-ui, -apple-system, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.container {
    width: 100%;
    max-width: 1140px;
    margin: 0 auto;
    padding: 0 16px;
}

.site-main { flex: 1 0 auto; }

h1 { font-size: 1.9rem; color: var(--primary); margin: 0 0 12px; }
h2 { font-size: 1.35rem; color: var(--primary); margin: 28px 0 12px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible {
    outline: 3px solid var(--accent);
    outline-offset: 2px;
}

.muted { color: var(--muted); }
.sr-only {
    position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
    overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

/* ---------- Header / navigation ---------- */

.site-header {
    background: var(--primary);
    color: #fff;
    position: sticky;
    top: 0;
    z-index: 50;
    box-shadow: var(--shadow);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-height: 62px;
    gap: 12px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
    color: #fff;
    font-weight: 700;
    font-size: 1.15rem;
}
.brand:hover { text-decoration: none; }

.brand-logo-img {
    height: 40px;
    width: auto;
    background: #fff;
    border-radius: 8px;
    padding: 4px 8px;
}

.main-nav ul {
    list-style: none;
    display: flex;
    align-items: center;
    gap: 4px;
    margin: 0;
    padding: 0;
}

.main-nav a {
    color: #dfe9f7;
    padding: 8px 12px;
    border-radius: 6px;
    font-size: 0.95rem;
    display: inline-block;
}
.main-nav a:hover, .main-nav a.active { background: rgba(255, 255, 255, 0.14); color: #fff; text-decoration: none; }
.main-nav .nav-login { background: var(--accent); color: #fff; }
.main-nav .nav-admin { border: 1px solid rgba(255, 255, 255, 0.4); }

.nav-toggle {
    display: none;
    background: none;
    border: 0;
    cursor: pointer;
    padding: 10px;
}
.nav-toggle span {
    display: block;
    width: 24px;
    height: 3px;
    background: #fff;
    margin: 5px 0;
    border-radius: 2px;
}

/* ---------- Hero ---------- */

.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: #fff;
    padding: 72px 0;
    text-align: center;
}
.hero h1 { color: #fff; font-size: 2.4rem; margin: 8px 0 14px; letter-spacing: 1px; }
.hero-symbols { color: #9fc1ee; font-size: 1rem; letter-spacing: 2px; margin: 0; }
.hero-subtitle { font-size: 1.15rem; color: #cfe0f5; max-width: 640px; margin: 0 auto 26px; }

/* ---------- Sections / cards ---------- */

.section { padding: 48px 0; }
.section-alt { background: #fff; }
.section-title { text-align: center; margin-bottom: 28px; }

.grade-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
}

.grade-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 26px 20px;
    text-align: center;
}
.grade-badge {
    width: 60px;
    height: 60px;
    margin: 0 auto 12px;
    border-radius: 50%;
    background: var(--accent-light);
    color: var(--primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1.15rem;
}
.grade-card h3 { margin: 0 0 6px; color: var(--primary); }
.grade-count { color: var(--muted); margin: 0 0 16px; }

.about-inner { max-width: 760px; margin: 0 auto; text-align: center; }
.feature-list {
    list-style: none;
    padding: 0;
    margin: 20px 0 0;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 10px;
}
.feature-list li {
    background: var(--accent-light);
    border-radius: 8px;
    padding: 10px 14px;
    color: var(--primary);
    font-weight: 600;
}

/* ---------- Buttons ---------- */

.btn {
    display: inline-block;
    border: 0;
    border-radius: 8px;
    padding: 11px 22px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    text-align: center;
    line-height: 1.2;
}
.btn:hover { text-decoration: none; filter: brightness(1.06); }
.btn-primary { background: var(--accent); color: #fff; }
.btn-outline { background: transparent; border: 1px solid var(--accent); color: var(--accent); }
.btn-danger { background: var(--danger); color: #fff; }
.btn-lg { padding: 15px 34px; font-size: 1.05rem; }
.btn-sm { padding: 6px 12px; font-size: 0.85rem; }
.btn-block { display: block; width: 100%; }

/* ---------- Auth ---------- */

.login-body {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    justify-content: center;
}

.auth-container {
    display: flex;
    justify-content: center;
    padding: 48px 16px;
    width: 100%;
}

.auth-card {
    background: var(--card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 34px 30px;
    width: 100%;
    max-width: 420px;
}
.auth-card h1 { margin-top: 0; }
.auth-sub { color: var(--muted); margin-top: -6px; }
.auth-logo { text-align: center; margin-bottom: 14px; }
.auth-logo img { max-width: 200px; height: auto; }

.error-card { text-align: center; max-width: 520px; }
.error-code { font-size: 3.4rem; font-weight: 800; color: var(--accent); margin: 0; }

/* ---------- Alerts ---------- */

.alert {
    border-radius: 8px;
    padding: 12px 16px;
    margin: 14px 0;
    border: 1px solid transparent;
}
.alert-success { background: #e5f6ee; border-color: #b9e6cf; color: var(--success); }
.alert-error { background: #fdeceb; border-color: #f5c6c0; color: var(--danger); }

/* ---------- Forms ---------- */

.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-weight: 600; margin-bottom: 6px; }
.form-group small { color: var(--muted); font-weight: 400; }

input[type="text"], input[type="password"], input[type="search"],
input[type="number"], input[type="file"], select, textarea {
    width: 100%;
    padding: 11px 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    font-family: var(--font);
    background: #fff;
    color: var(--text);
}
textarea { resize: vertical; }

.admin-form {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 24px;
    max-width: 640px;
}

.filter-form {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin: 16px 0;
}
.filter-form input, .filter-form select { width: auto; flex: 1 1 160px; }

.search-form {
    display: flex;
    gap: 10px;
    margin: 16px 0 24px;
}
.search-form input { flex: 1; }

/* ---------- Stats / progress ---------- */

.stat-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 14px;
    margin: 22px 0;
}

.stat-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 18px;
    text-align: center;
}
.stat-number { display: block; font-size: 1.8rem; font-weight: 800; color: var(--primary); }
.stat-label { color: var(--muted); font-size: 0.9rem; }

.progress-block { margin: 26px 0; }
.progress-bar {
    background: #e2e8f0;
    border-radius: 99px;
    height: 18px;
    overflow: hidden;
}
.progress-fill {
    background: linear-gradient(90deg, var(--accent), var(--success));
    height: 100%;
    border-radius: 99px;
    transition: width 0.4s ease;
}
.progress-bar-sm { height: 10px; margin-bottom: 4px; }

.continue-block {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 22px;
}

/* ---------- Lesson cards ---------- */

.lesson-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 18px;
}

.lesson-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 20px;
    display: flex;
    flex-direction: column;
}
.lesson-number {
    font-size: 1.6rem;
    font-weight: 800;
    color: var(--accent);
    margin-bottom: 6px;
}
.lesson-title { font-size: 1.1rem; margin: 0 0 4px; color: var(--primary); }
.lesson-meta { color: var(--muted); font-size: 0.88rem; margin: 0 0 10px; }
.lesson-status { margin: 0 0 14px; }
.lesson-card .btn { margin-top: auto; }

.status { font-weight: 700; font-size: 0.88rem; }
.status-done { color: var(--success); }
.status-progress { color: var(--warning); }
.status-todo { color: var(--muted); }

/* ---------- Lesson page / video ---------- */

.lesson-page { max-width: 900px; }
.lesson-breadcrumb { margin: 6px 0 0; }

.video-container {
    position: relative;
    width: 100%;
    aspect-ratio: 16 / 9;
    background: #000;
    border-radius: var(--radius);
    overflow: hidden;
    margin: 18px 0;
}
.video-frame, #ytPlayer {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

.lesson-body {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 22px;
    margin-bottom: 20px;
}

.lesson-nav {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    margin: 16px 0;
}

.topic-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 18px;
}
.topic-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 20px;
}
.topic-card h2 { margin-top: 0; font-size: 1.15rem; }

/* ---------- Tables ---------- */

.table-container {
    overflow-x: auto;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.data-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.93rem;
}
.data-table th, .data-table td {
    text-align: left;
    padding: 11px 14px;
    border-bottom: 1px solid var(--border);
    white-space: nowrap;
}
.data-table th { background: var(--accent-light); color: var(--primary); }
.data-table tr:last-child td { border-bottom: 0; }

.actions { display: flex; gap: 6px; flex-wrap: wrap; }
.inline-form { display: inline; margin: 0; }

/* ---------- Pagination ---------- */

.pagination { display: flex; gap: 6px; margin: 18px 0; flex-wrap: wrap; }
.pagination a {
    padding: 7px 13px;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: #fff;
    color: var(--text);
}
.pagination a.active { background: var(--accent); border-color: var(--accent); color: #fff; }

/* ---------- Admin layout ---------- */

.admin-body { flex-direction: row; background: var(--bg); }

.admin-sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: 240px;
    background: var(--primary);
    color: #fff;
    padding: 18px 0;
    overflow-y: auto;
    z-index: 60;
}
.admin-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
    padding: 0 20px 18px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.15);
    margin-bottom: 12px;
}
.admin-menu { list-style: none; margin: 0; padding: 0; }
.admin-menu a {
    display: block;
    color: #dfe9f7;
    padding: 11px 20px;
    font-size: 0.95rem;
}
.admin-menu a:hover, .admin-menu a.active { background: rgba(255, 255, 255, 0.14); color: #fff; text-decoration: none; }

.admin-content {
    margin-left: 240px;
    padding: 28px;
    flex: 1;
    min-width: 0;
}

.admin-header-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
}

.admin-toggle { position: fixed; top: 10px; right: 12px; z-index: 80; background: var(--accent); border-radius: 8px; }

.video-preview { margin-bottom: 16px; }

/* ---------- Footer ---------- */

.site-footer {
    background: var(--primary-dark);
    color: #b9cbe4;
    padding: 22px 0;
    text-align: center;
    margin-top: 40px;
}
.footer-inner p { margin: 4px 0; }
.footer-link { color: #9fc1ee; }
.footer-math { letter-spacing: 6px; color: #7d9cc9; }