/* ================================================
   LMS Common Styles - Codeit Inspired Design
   Responsive & Modern UI System
   ================================================ */

/* CSS Variables - Design Tokens */
:root {
    /* Primary Colors */
    --primary-blue: #3182F6;
    --primary-blue-hover: #1B64DA;
    --primary-blue-light: #E8F3FF;

    /* Category Colors */
    --color-coding: #3182F6;
    --color-data: #F59E0B;
    --color-programming: #8B5CF6;
    --color-ml: #10B981;
    --color-web: #EC4899;
    --color-mobile: #06B6D4;

    /* Neutral Colors */
    --gray-50: #F9FAFB;
    --gray-100: #F3F4F6;
    --gray-200: #E5E7EB;
    --gray-300: #D1D5DB;
    --gray-400: #9CA3AF;
    --gray-500: #6B7280;
    --gray-600: #4B5563;
    --gray-700: #374151;
    --gray-800: #1F2937;
    --gray-900: #111827;

    /* Semantic Colors */
    --success: #10B981;
    --success-light: #D1FAE5;
    --warning: #F59E0B;
    --warning-light: #FEF3C7;
    --error: #EF4444;
    --error-light: #FEE2E2;

    /* Background */
    --bg-primary: #FFFFFF;
    --bg-secondary: #F9FAFB;
    --bg-tertiary: #F3F4F6;

    /* Typography */
    --font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;

    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-2xl: 24px;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;

    /* Container */
    --container-max: 1200px;
    --header-height: 64px;
}

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    color: var(--gray-800);
    background-color: var(--bg-secondary);
    line-height: 1.6;
    min-height: 100vh;
}

a {
    color: inherit;
    text-decoration: none;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

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

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

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    color: var(--gray-900);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

@media (max-width: 768px) {
    h1 { font-size: 1.875rem; }
    h2 { font-size: 1.5rem; }
    h3 { font-size: 1.25rem; }
}

/* Container */
.container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--space-md);
}

@media (min-width: 768px) {
    .container {
        padding: 0 var(--space-lg);
    }
}

/* ================================================
   Header / Navigation
   ================================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--bg-primary);
    border-bottom: 1px solid var(--gray-200);
    z-index: 1000;
    display: flex;
    align-items: center;
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.header-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary-blue);
}

.header-logo span {
    background: linear-gradient(135deg, var(--primary-blue), var(--color-programming));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-nav {
    display: none;
    gap: var(--space-xl);
}

@media (min-width: 768px) {
    .header-nav {
        display: flex;
    }
}

.header-nav a {
    font-weight: 500;
    color: var(--gray-600);
    transition: color var(--transition-fast);
}

.header-nav a:hover {
    color: var(--primary-blue);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

/* Mobile Menu Button */
.mobile-menu-btn {
    display: flex;
    flex-direction: column;
    gap: 5px;
    padding: var(--space-sm);
}

@media (min-width: 768px) {
    .mobile-menu-btn {
        display: none;
    }
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--gray-700);
    transition: var(--transition-fast);
}

/* Mobile Navigation */
.mobile-nav {
    display: none;
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-primary);
    padding: var(--space-lg);
    z-index: 999;
}

.mobile-nav.active {
    display: block;
}

.mobile-nav a {
    display: block;
    padding: var(--space-md) 0;
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--gray-700);
    border-bottom: 1px solid var(--gray-200);
}

/* ================================================
   Buttons
   ================================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    font-size: 0.9375rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.875rem;
}

.btn-lg {
    padding: var(--space-md) var(--space-xl);
    font-size: 1rem;
}

.btn-xl {
    padding: var(--space-md) var(--space-2xl);
    font-size: 1.125rem;
    border-radius: var(--radius-lg);
}

.btn-primary {
    background: var(--primary-blue);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-blue-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--gray-100);
    color: var(--gray-700);
}

.btn-secondary:hover {
    background: var(--gray-200);
}

.btn-outline {
    border: 1px solid var(--gray-300);
    background: transparent;
    color: var(--gray-700);
}

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

.btn-ghost {
    background: transparent;
    color: var(--gray-600);
}

.btn-ghost:hover {
    background: var(--gray-100);
    color: var(--gray-800);
}

.btn-danger {
    background: var(--error);
    color: white;
}

.btn-danger:hover {
    background: #DC2626;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.btn-block {
    width: 100%;
}

/* ================================================
   Form Elements
   ================================================ */
.form-group {
    margin-bottom: var(--space-lg);
}

.form-label {
    display: block;
    margin-bottom: var(--space-sm);
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--gray-700);
}

.form-label .required {
    color: var(--error);
    margin-left: 2px;
}

.form-input {
    width: 100%;
    padding: var(--space-md);
    font-size: 1rem;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    transition: all var(--transition-fast);
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px var(--primary-blue-light);
}

.form-input::placeholder {
    color: var(--gray-400);
}

.form-input:disabled {
    background: var(--gray-100);
    cursor: not-allowed;
}

.form-input.error {
    border-color: var(--error);
}

.form-input.error:focus {
    box-shadow: 0 0 0 3px var(--error-light);
}

.form-select {
    width: 100%;
    padding: var(--space-md);
    font-size: 1rem;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%236B7280' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    background-size: 16px;
    padding-right: 40px;
}

.form-select:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px var(--primary-blue-light);
}

.form-checkbox {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    cursor: pointer;
}

.form-checkbox input[type="checkbox"] {
    width: 18px;
    height: 18px;
    border-radius: 4px;
    accent-color: var(--primary-blue);
    cursor: pointer;
}

.form-checkbox span {
    font-size: 0.9375rem;
    color: var(--gray-600);
}

.form-hint {
    margin-top: var(--space-xs);
    font-size: 0.875rem;
    color: var(--gray-500);
}

.form-error {
    margin-top: var(--space-xs);
    font-size: 0.875rem;
    color: var(--error);
}

/* ================================================
   Cards
   ================================================ */
.card {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.card-image {
    width: 100%;
    aspect-ratio: 16/9;
    background: var(--gray-100);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--gray-400);
    font-size: 0.875rem;
}

.card-body {
    padding: var(--space-lg);
}

.card-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
    color: var(--gray-900);
}

.card-text {
    font-size: 0.9375rem;
    color: var(--gray-600);
    line-height: 1.5;
}

.card-footer {
    padding: var(--space-md) var(--space-lg);
    border-top: 1px solid var(--gray-100);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Category Card */
.category-card {
    background: var(--bg-primary);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    text-align: center;
    transition: all var(--transition-normal);
    border: 1px solid var(--gray-200);
}

.category-card:hover {
    border-color: var(--primary-blue);
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.category-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--space-md);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    background: var(--gray-100);
}

.category-card.blue .category-icon { background: #E8F3FF; color: var(--color-coding); }
.category-card.yellow .category-icon { background: #FEF3C7; color: var(--color-data); }
.category-card.purple .category-icon { background: #EDE9FE; color: var(--color-programming); }
.category-card.green .category-icon { background: #D1FAE5; color: var(--color-ml); }
.category-card.pink .category-icon { background: #FCE7F3; color: var(--color-web); }
.category-card.cyan .category-icon { background: #CFFAFE; color: var(--color-mobile); }

.category-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--gray-800);
}

/* ================================================
   Alerts & Messages
   ================================================ */
.alert {
    padding: var(--space-md);
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    display: none;
}

.alert.show {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.alert-success {
    background: var(--success-light);
    color: #065F46;
    border: 1px solid #A7F3D0;
}

.alert-error {
    background: var(--error-light);
    color: #991B1B;
    border: 1px solid #FECACA;
}

.alert-warning {
    background: var(--warning-light);
    color: #92400E;
    border: 1px solid #FDE68A;
}

.alert-info {
    background: var(--primary-blue-light);
    color: #1E40AF;
    border: 1px solid #BFDBFE;
}

/* ================================================
   Badges
   ================================================ */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 4px 10px;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: var(--radius-full);
}

.badge-primary {
    background: var(--primary-blue-light);
    color: var(--primary-blue);
}

.badge-success {
    background: var(--success-light);
    color: var(--success);
}

.badge-warning {
    background: var(--warning-light);
    color: var(--warning);
}

.badge-error {
    background: var(--error-light);
    color: var(--error);
}

.badge-gray {
    background: var(--gray-100);
    color: var(--gray-600);
}

/* Role Badges */
.role-badge {
    padding: 6px 14px;
    font-size: 0.8125rem;
    font-weight: 600;
    border-radius: var(--radius-full);
}

.role-badge.ADMIN {
    background: linear-gradient(135deg, #EF4444, #DC2626);
    color: white;
}

.role-badge.PROFESSOR {
    background: linear-gradient(135deg, #8B5CF6, #7C3AED);
    color: white;
}

.role-badge.STUDENT {
    background: linear-gradient(135deg, #10B981, #059669);
    color: white;
}

/* ================================================
   Hero Section
   ================================================ */
.hero {
    padding: calc(var(--header-height) + var(--space-3xl)) 0 var(--space-3xl);
    background: linear-gradient(180deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
}

.hero-content {
    text-align: center;
    max-width: 720px;
    margin: 0 auto;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: var(--space-lg);
    color: var(--gray-900);
}

.hero-title .highlight {
    background: linear-gradient(135deg, var(--primary-blue), var(--color-programming));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--gray-600);
    margin-bottom: var(--space-xl);
    line-height: 1.7;
}

.hero-actions {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    align-items: center;
}

@media (min-width: 480px) {
    .hero-actions {
        flex-direction: row;
        justify-content: center;
    }
}

@media (min-width: 768px) {
    .hero-title {
        font-size: 3.5rem;
    }

    .hero-description {
        font-size: 1.25rem;
    }
}

/* ================================================
   Section
   ================================================ */
.section {
    padding: var(--space-3xl) 0;
}

.section-header {
    text-align: center;
    margin-bottom: var(--space-2xl);
}

.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: var(--space-sm);
}

.section-subtitle {
    font-size: 1rem;
    color: var(--gray-500);
}

@media (min-width: 768px) {
    .section-title {
        font-size: 2rem;
    }
}

/* ================================================
   Grid System
   ================================================ */
.grid {
    display: grid;
    gap: var(--space-lg);
}

.grid-2 { grid-template-columns: repeat(1, 1fr); }
.grid-3 { grid-template-columns: repeat(1, 1fr); }
.grid-4 { grid-template-columns: repeat(2, 1fr); }

@media (min-width: 640px) {
    .grid-2 { grid-template-columns: repeat(2, 1fr); }
    .grid-3 { grid-template-columns: repeat(2, 1fr); }
    .grid-4 { grid-template-columns: repeat(2, 1fr); }
}

@media (min-width: 768px) {
    .grid-3 { grid-template-columns: repeat(3, 1fr); }
    .grid-4 { grid-template-columns: repeat(4, 1fr); }
}

/* ================================================
   Auth Container (Login/Register/Withdraw)
   ================================================ */
.auth-page {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-lg);
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

.auth-container {
    width: 100%;
    max-width: 440px;
}

.auth-card {
    background: var(--bg-primary);
    border-radius: var(--radius-2xl);
    box-shadow: var(--shadow-xl);
    padding: var(--space-2xl);
}

@media (min-width: 480px) {
    .auth-card {
        padding: var(--space-2xl) var(--space-3xl);
    }
}

.auth-header {
    text-align: center;
    margin-bottom: var(--space-xl);
}

.auth-logo {
    font-size: 2rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary-blue), var(--color-programming));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-sm);
}

.auth-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: var(--space-xs);
}

.auth-subtitle {
    font-size: 0.9375rem;
    color: var(--gray-500);
}

.auth-form .form-group:last-of-type {
    margin-bottom: var(--space-lg);
}

.auth-footer {
    text-align: center;
    margin-top: var(--space-lg);
    padding-top: var(--space-lg);
    border-top: 1px solid var(--gray-200);
}

.auth-footer a {
    color: var(--primary-blue);
    font-weight: 500;
    transition: color var(--transition-fast);
}

.auth-footer a:hover {
    color: var(--primary-blue-hover);
    text-decoration: underline;
}

.auth-links {
    display: flex;
    justify-content: center;
    gap: var(--space-lg);
    margin-top: var(--space-md);
}

.auth-divider {
    display: flex;
    align-items: center;
    margin: var(--space-lg) 0;
    color: var(--gray-400);
    font-size: 0.875rem;
}

.auth-divider::before,
.auth-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--gray-200);
}

.auth-divider span {
    padding: 0 var(--space-md);
}

/* ================================================
   Dashboard Layout
   ================================================ */
.dashboard {
    padding-top: var(--header-height);
    min-height: 100vh;
}

.dashboard-content {
    padding: var(--space-xl) 0;
}

.dashboard-welcome {
    background: linear-gradient(135deg, var(--primary-blue), var(--color-programming));
    color: white;
    padding: var(--space-2xl);
    border-radius: var(--radius-2xl);
    margin-bottom: var(--space-xl);
}

.dashboard-welcome h2 {
    font-size: 1.75rem;
    color: white;
    margin-bottom: var(--space-sm);
}

.dashboard-welcome p {
    opacity: 0.9;
    font-size: 1rem;
}

.dashboard-stats {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-md);
    margin-bottom: var(--space-xl);
}

@media (min-width: 768px) {
    .dashboard-stats {
        grid-template-columns: repeat(4, 1fr);
    }
}

.stat-card {
    background: var(--bg-primary);
    padding: var(--space-lg);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-sm);
    text-align: center;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-blue);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--gray-500);
    margin-top: var(--space-xs);
}

/* ================================================
   Footer
   ================================================ */
.footer {
    background: var(--gray-900);
    color: var(--gray-400);
    padding: var(--space-2xl) 0;
}

.footer-content {
    display: grid;
    gap: var(--space-xl);
}

@media (min-width: 768px) {
    .footer-content {
        grid-template-columns: 2fr 1fr 1fr 1fr;
    }
}

.footer-brand {
    font-size: 1.5rem;
    font-weight: 800;
    color: white;
    margin-bottom: var(--space-md);
}

.footer-description {
    font-size: 0.9375rem;
    line-height: 1.6;
}

.footer-title {
    font-size: 1rem;
    font-weight: 600;
    color: white;
    margin-bottom: var(--space-md);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--space-sm);
}

.footer-links a {
    font-size: 0.9375rem;
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: white;
}

.footer-bottom {
    border-top: 1px solid var(--gray-800);
    margin-top: var(--space-xl);
    padding-top: var(--space-lg);
    text-align: center;
    font-size: 0.875rem;
}

/* ================================================
   Utilities
   ================================================ */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.text-primary { color: var(--primary-blue); }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-error { color: var(--error); }
.text-gray { color: var(--gray-500); }

.mb-0 { margin-bottom: 0; }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

.mt-0 { margin-top: 0; }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }

.hidden { display: none; }
.visible { display: block; }

@media (max-width: 767px) {
    .hide-mobile { display: none; }
}

@media (min-width: 768px) {
    .hide-desktop { display: none; }
}

/* Loading Spinner */
.spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Skeleton Loading */
.skeleton {
    background: linear-gradient(90deg, var(--gray-200) 25%, var(--gray-100) 50%, var(--gray-200) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: var(--radius-md);
}

@keyframes shimmer {
    0% { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}