/* ==========================================================================
   ACS — All Computer Skills
   Design System & Main Stylesheet (Vanilla CSS)
   ========================================================================== */

:root {
    /* Palette Colors from Image */
    --color-001d39: #001D39;
    --color-0a4174: #0A4174;
    --color-49769f: #49769F;
    --color-4e8ea2: #4E8EA2;
    --color-6ea2b3: #6EA2B3;
    --color-7bbde8: #7BBDE8;
    --color-bdd8e9: #BDD8E9;

    /* Theme Tokens - Light Mode */
    --bg-page: #F0F5FA;
    --color-bg: #F0F5FA;
    --color-surface: #FFFFFF;
    --color-surface-hover: #E8F1F8;
    --color-surface-alt: #E1ECF4;
    --color-border: #CBDDE9;
    --color-border-focus: var(--color-0a4174);
    
    --color-text-main: var(--color-001d39);
    --color-text-muted: var(--color-49769f);
    --color-text-light: #6E8EA6;

    --brand-navy: var(--color-001d39);
    --brand-blue: var(--color-0a4174);
    --brand-blue-hover: #08335C;
    --brand-blue-light: #E6EFF7;
    --brand-cyan: var(--color-7bbde8);
    --brand-gold: #F5C451;

    --color-success: #0E9F6E;
    --color-success-bg: #E3F8EE;
    --color-warning: #D97706;
    --color-warning-bg: #FEF3C7;
    --color-danger: #DC2626;
    --color-danger-bg: #FEE2E2;

    --shadow-sm: 0 1px 3px rgba(0, 29, 57, 0.06);
    --shadow-md: 0 4px 10px -1px rgba(0, 29, 57, 0.09), 0 2px 4px -2px rgba(0, 29, 57, 0.05);
    --shadow-lg: 0 12px 20px -3px rgba(0, 29, 57, 0.12);

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-full: 9999px;

    --container-max: 1200px;
    --header-height: 72px;
    --sidebar-width: 260px;
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

    /* Header Compatibility Variables */
    --bg-header: var(--color-surface);
    --bg-surface: var(--color-surface);
    --bg-surface-subtle: var(--color-surface-hover);
    --text-color: var(--color-text-main);
    --text-muted: var(--color-text-muted);
    --border-color: var(--color-border);
    --bg-hover: var(--color-surface-hover);
    --secondary-bg: var(--color-surface);
    --secondary-hover: var(--color-surface-hover);
    --nav-hover-bg: var(--color-surface-hover);
    --nav-active-bg: var(--brand-blue-light);
    --primary-color: var(--brand-blue);
    --primary-hover: var(--brand-blue-hover);
    --border-hover: var(--color-49769f);
}

/* Dark Mode Tokens */
[data-theme="dark"] {
    --color-bg: #001224;
    --color-surface: #001D39;
    --color-surface-hover: #072B52;
    --color-surface-alt: #0A3663;
    --color-border: #133E68;
    --color-border-focus: var(--color-7bbde8);

    --color-text-main: #F0F6FC;
    --color-text-muted: #9BB8D3;
    --color-text-light: #6E8EA6;

    --brand-blue-light: rgba(123, 189, 232, 0.15);
    --brand-blue: #3E8AC7;
    --brand-blue-hover: #7BBDE8;

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 10px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 12px 22px rgba(0, 0, 0, 0.6);

    --color-success-bg: rgba(14, 159, 110, 0.2);
    --color-warning-bg: rgba(217, 119, 6, 0.2);
    --color-danger-bg: rgba(220, 38, 38, 0.2);

    --bg-header: var(--color-surface);
    --bg-surface: var(--color-surface);
    --bg-surface-subtle: var(--color-surface-hover);
    --text-color: var(--color-text-main);
    --text-muted: var(--color-text-muted);
    --border-color: var(--color-border);
    --bg-hover: var(--color-surface-hover);
    --secondary-bg: var(--color-surface);
    --secondary-hover: var(--color-surface-hover);
    --nav-hover-bg: var(--color-surface-hover);
    --nav-active-bg: rgba(123, 189, 232, 0.12);
    --primary-color: var(--color-7bbde8);
    --primary-hover: #A5D3F2;
    --border-hover: var(--color-7bbde8);
}

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

html {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text-main);
    background-color: var(--color-bg);
    transition: background-color 0.2s ease, color 0.2s ease;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
}

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

a {
    color: var(--brand-blue);
    text-decoration: none;
    transition: color 0.15s ease;
}

a:hover {
    color: var(--brand-blue-hover);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

button, input, select, textarea {
    font-family: inherit;
    font-size: inherit;
    color: inherit;
}

.container {
    width: 100%;
    max-width: var(--container-max);
    margin-left: auto;
    margin-right: auto;
    padding-left: 1.5rem;
    padding-right: 1.5rem;
}

.main-content {
    flex: 1;
    padding-top: 2rem;
    padding-bottom: 4rem;
}

/* Header & Navigation */
.site-header {
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 50;
    transition: background-color 0.2s ease, border-color 0.2s ease;
}

.header-inner {
    height: var(--header-height);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1.5rem;
}

.brand-logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none;
    color: var(--color-text-main);
}

.brand-badge {
    background: linear-gradient(135deg, var(--color-0a4174), var(--color-7bbde8));
    color: #FFFFFF;
    font-weight: 800;
    font-size: 1.15rem;
    padding: 0.35rem 0.65rem;
    border-radius: var(--radius-sm);
    letter-spacing: 0.05em;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.brand-details {
    display: flex;
    flex-direction: column;
}

.brand-name {
    font-size: 1.15rem;
    font-weight: 700;
    letter-spacing: -0.01em;
    line-height: 1.2;
}

.brand-tagline {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-49769f);
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 1.75rem;
    list-style: none;
}

.nav-link {
    font-weight: 500;
    color: var(--color-text-muted);
    font-size: 0.95rem;
    padding: 0.4rem 0.1rem;
    position: relative;
    transition: color 0.15s ease;
}

.nav-link:hover, .nav-link.active {
    color: var(--brand-blue);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    right: 0;
    height: 2px;
    background-color: var(--brand-blue);
    border-radius: 2px;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 0.85rem;
}

.theme-toggle-btn {
    background: transparent;
    border: 1px solid var(--color-border);
    color: var(--color-text-muted);
    width: 38px;
    height: 38px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
}

.theme-toggle-btn:hover {
    color: var(--color-text-main);
    border-color: var(--color-text-muted);
    background-color: var(--color-surface-hover);
}

.theme-toggle-btn svg {
    width: 18px;
    height: 18px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    font-weight: 600;
    font-size: 0.925rem;
    border-radius: var(--radius-sm);
    border: 1px solid transparent;
    cursor: pointer;
    text-align: center;
    text-decoration: none;
    transition: all 0.15s ease-in-out;
    line-height: 1.25;
}

.btn-primary {
    background-color: var(--brand-blue);
    color: #FFFFFF;
}

.btn-primary:hover {
    background-color: var(--brand-blue-hover);
    color: #FFFFFF;
}

.btn-secondary {
    background-color: var(--color-surface);
    color: var(--color-text-main);
    border-color: var(--color-border);
}

.btn-secondary:hover {
    background-color: var(--color-surface-hover);
    border-color: var(--color-49769f);
    color: var(--color-text-main);
}

.btn-outline {
    background-color: transparent;
    color: var(--brand-blue);
    border-color: var(--brand-blue);
}

.btn-outline:hover {
    background-color: var(--brand-blue-light);
    color: var(--brand-blue);
}

.btn-sm {
    padding: 0.4rem 0.85rem;
    font-size: 0.85rem;
}

.btn-lg {
    padding: 0.85rem 1.75rem;
    font-size: 1rem;
}

.btn-danger {
    background-color: var(--color-danger);
    color: #FFFFFF;
}

.btn-danger:hover {
    background-color: #B91C1C;
    color: #FFFFFF;
}

.btn-success {
    background-color: var(--color-success);
    color: #FFFFFF;
}

.btn-block {
    width: 100%;
}

/* Cards & Surfaces */
.card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.card:hover {
    border-color: var(--color-7bbde8);
    box-shadow: var(--shadow-md);
}

.card-body {
    padding: 1.5rem;
}

.card-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.card-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--color-border);
    background-color: var(--color-surface-hover);
}

/* Course Grid */
.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.75rem;
}

.course-card {
    display: flex;
    flex-direction: column;
    height: 100%;
}

.course-thumbnail-wrapper {
    position: relative;
    width: 100%;
    aspect-ratio: 16 / 9;
    background-color: var(--color-surface-alt);
    overflow: hidden;
}

.course-thumbnail {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s ease;
}

.course-card:hover .course-thumbnail {
    transform: scale(1.03);
}

.course-type-badge {
    position: absolute;
    top: 12px;
    right: 12px;
    padding: 0.25rem 0.65rem;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    border-radius: var(--radius-sm);
    backdrop-filter: blur(8px);
}

.badge-free {
    background-color: rgba(14, 159, 110, 0.95);
    color: #FFFFFF;
}

.badge-paid {
    background-color: rgba(10, 65, 116, 0.95);
    color: #FFFFFF;
}

.course-card-content {
    padding: 1.35rem;
    display: flex;
    flex-direction: column;
    flex: 1;
}

.course-category {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--brand-blue);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.5rem;
}

.course-card-title {
    font-size: 1.15rem;
    font-weight: 700;
    line-height: 1.35;
    margin-bottom: 0.6rem;
    color: var(--color-text-main);
}

.course-card-desc {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    line-height: 1.5;
    margin-bottom: 1.25rem;
    flex: 1;
}

.course-card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 1rem;
    border-top: 1px solid var(--color-border);
}

.course-price-wrap {
    display: flex;
    align-items: baseline;
    gap: 0.4rem;
}

.price-current {
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--color-text-main);
}

.price-original {
    font-size: 0.9rem;
    color: var(--color-text-light);
    text-decoration: line-through;
}

/* Hero Section */
.hero-section {
    padding: 4.5rem 0 3.5rem;
    text-align: center;
    background: radial-gradient(circle at 50% 20%, var(--brand-blue-light) 0%, transparent 65%);
}

.hero-tagline {
    display: inline-block;
    font-size: 0.825rem;
    font-weight: 700;
    letter-spacing: 0.15em;
    text-transform: uppercase;
    color: var(--brand-blue);
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    padding: 0.35rem 1rem;
    border-radius: var(--radius-full);
    margin-bottom: 1.25rem;
    box-shadow: var(--shadow-sm);
}

.hero-title {
    font-size: 2.75rem;
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.025em;
    color: var(--color-text-main);
    max-width: 800px;
    margin: 0 auto 1.25rem;
}

.hero-description {
    font-size: 1.15rem;
    line-height: 1.6;
    color: var(--color-text-muted);
    max-width: 680px;
    margin: 0 auto 2.25rem;
}

.hero-cta-group {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Category Pills */
.category-strip {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    flex-wrap: wrap;
    margin: 2.5rem 0 1rem;
}

.category-chip {
    padding: 0.5rem 1rem;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    color: var(--color-text-muted);
    font-size: 0.875rem;
    font-weight: 600;
    transition: all 0.15s ease;
}

.category-chip:hover, .category-chip.active {
    background-color: var(--brand-blue);
    border-color: var(--brand-blue);
    color: #FFFFFF;
}

/* Forms */
.form-group {
    margin-bottom: 1.25rem;
}

.form-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 0.4rem;
    color: var(--color-text-main);
}

.form-control {
    width: 100%;
    padding: 0.625rem 0.875rem;
    font-size: 0.95rem;
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    color: var(--color-text-main);
    transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.form-control:focus {
    outline: none;
    border-color: var(--color-border-focus);
    box-shadow: 0 0 0 3px rgba(10, 65, 116, 0.18);
}

textarea.form-control {
    min-height: 120px;
    resize: vertical;
}

.form-hint {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-top: 0.35rem;
}

/* Alerts */
.alert {
    padding: 0.85rem 1.25rem;
    border-radius: var(--radius-sm);
    font-size: 0.925rem;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    line-height: 1.5;
}

.alert-success {
    background-color: var(--color-success-bg);
    color: #065F46;
    border: 1px solid rgba(14, 159, 110, 0.35);
}

.alert-danger {
    background-color: var(--color-danger-bg);
    color: #991B1B;
    border: 1px solid rgba(220, 38, 38, 0.35);
}

.alert-warning {
    background-color: var(--color-warning-bg);
    color: #92400E;
    border: 1px solid rgba(217, 119, 6, 0.35);
}

.alert-info {
    background-color: var(--brand-blue-light);
    color: var(--color-0a4174);
    border: 1px solid var(--color-bdd8e9);
}

[data-theme="dark"] .alert-success { color: #34D399; }
[data-theme="dark"] .alert-danger { color: #F87171; }
[data-theme="dark"] .alert-warning { color: #FBBF24; }
[data-theme="dark"] .alert-info { color: #7BBDE8; }

/* Footer */
.site-footer {
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: 3rem 0 1.5rem;
    margin-top: auto;
    font-size: 0.9rem;
    color: var(--color-text-muted);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 2.5rem;
    margin-bottom: 2.5rem;
}

.footer-col-title {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--color-text-main);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.footer-links {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

.footer-links a {
    color: var(--color-text-muted);
}

.footer-links a:hover {
    color: var(--brand-blue);
}

.footer-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 1.5rem;
    border-top: 1px solid var(--color-border);
    font-size: 0.85rem;
}

/* Mobile Nav Drawer */
.mobile-nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: space-around;
    width: 38px;
    height: 38px;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 8px;
    cursor: pointer;
}

.hamburger-bar {
    width: 100%;
    height: 2px;
    background-color: currentColor;
    border-radius: 2px;
    transition: transform 0.25s ease, opacity 0.25s ease;
}

.mobile-nav-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 29, 57, 0.45);
    backdrop-filter: blur(3px);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease;
    z-index: 1040;
}

.mobile-nav-backdrop.open {
    opacity: 1;
    visibility: visible;
}

.mobile-nav-drawer {
    position: fixed;
    top: 0;
    right: -320px;
    width: 300px;
    max-width: 85vw;
    height: 100%;
    background: var(--bg-surface);
    color: var(--text-color);
    box-shadow: -4px 0 24px rgba(0, 29, 57, 0.18);
    display: flex;
    flex-direction: column;
    transition: right 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    z-index: 1050;
}

.mobile-nav-drawer.open {
    right: 0;
}

.mobile-drawer-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
}

.mobile-drawer-close {
    background: none;
    border: none;
    font-size: 28px;
    line-height: 1;
    cursor: pointer;
    color: inherit;
}

.mobile-drawer-body {
    flex: 1;
    overflow-y: auto;
    padding: 16px 0;
}

.mobile-menu-links {
    list-style: none;
    padding: 0;
    margin: 0;
}

.mobile-link {
    display: block;
    padding: 12px 24px;
    font-weight: 500;
    text-decoration: none;
    color: inherit;
    transition: background 0.2s ease, color 0.2s ease;
}

.mobile-link:hover,
.mobile-link.active {
    background: var(--nav-active-bg);
    color: var(--primary-color);
}

.drawer-divider {
    height: 1px;
    background: var(--border-color);
    margin: 12px 20px;
}

.drawer-section-label {
    padding: 6px 24px;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    opacity: 0.6;
}

.mobile-drawer-footer {
    padding: 16px 20px;
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 10px;
}

@media (max-width: 868px) {
    .desktop-nav, .desktop-auth { display: none; }
    .mobile-nav-toggle { display: flex; }
}

@media (max-width: 768px) {
    .hero-title { font-size: 2rem; }
    .course-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 2rem; }
    .footer-bottom { flex-direction: column; gap: 0.75rem; text-align: center; }
}