/* ===================================
   CSS Variables & Reset
   =================================== */
:root {
    /* Primary Colors - Tech Blue Theme */
    --primary-50: #eff6ff;
    --primary-100: #dbeafe;
    --primary-200: #bfdbfe;
    --primary-300: #93c5fd;
    --primary-400: #60a5fa;
    --primary-500: #3b82f6;
    --primary-600: #2563eb;
    --primary-700: #1d4ed8;
    --primary-800: #1e40af;
    --primary-900: #1e3a8a;
    
    /* Accent Colors */
    --accent-500: #8b5cf6;
    --accent-600: #7c3aed;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    
    /* 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;
    
    /* Dark Theme */
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 200ms ease;
    --transition-slow: 300ms ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; }
h3 { font-size: 1.875rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: var(--spacing-md);
    color: var(--text-secondary);
}

/* ===================================
   Layout
   =================================== */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.section {
    display: none;
    padding: var(--spacing-2xl) 0;
    min-height: calc(100vh - 80px);
    animation: fadeIn 0.3s ease;
}

.section.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===================================
   Navigation
   =================================== */
.navbar {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--bg-tertiary);
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 80px;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--text-primary);
}

.brand-icon {
    width: 32px;
    height: 32px;
    color: var(--primary-500);
}

.nav-menu {
    display: flex;
    gap: var(--spacing-sm);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
    font-weight: 500;
}

.nav-link:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.nav-link.active {
    background: var(--primary-600);
    color: white;
}

.nav-link i {
    width: 20px;
    height: 20px;
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: var(--spacing-sm);
}

.nav-toggle i {
    width: 24px;
    height: 24px;
}

/* ===================================
   Buttons
   =================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
}

.btn i {
    width: 20px;
    height: 20px;
}

.btn-primary {
    background: var(--primary-600);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-700);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--gray-600);
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.icon-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.icon-btn i {
    width: 18px;
    height: 18px;
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    padding: var(--spacing-2xl) 0;
}

.hero-content {
    text-align: center;
    max-width: 800px;
    margin: 0 auto var(--spacing-2xl);
}

.hero-title {
    font-size: 3.5rem;
    margin-bottom: var(--spacing-lg);
    line-height: 1.1;
}

.gradient-text {
    background: linear-gradient(135deg, var(--primary-400), var(--accent-500));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-description {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

.hero-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

.hero-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.stat-card {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
    transition: all var(--transition-base);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-600);
}

.stat-icon {
    width: 48px;
    height: 48px;
    color: var(--primary-500);
}

.stat-value {
    font-size: 2rem;
    font-weight: 800;
    color: var(--text-primary);
}

.stat-label {
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* ===================================
   Features Section
   =================================== */
.features {
    padding: var(--spacing-2xl) 0;
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    font-size: 2.5rem;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-xl);
}

.feature-card {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-600);
}

.feature-icon {
    width: 56px;
    height: 56px;
    background: linear-gradient(135deg, var(--primary-600), var(--accent-600));
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-lg);
}

.feature-icon i {
    width: 32px;
    height: 32px;
    color: white;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
}

.feature-card p {
    color: var(--text-secondary);
    margin: 0;
}

/* ===================================
   Compiler Section
   =================================== */
.compiler-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.compiler-controls {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.language-select {
    padding: 0.75rem 1rem;
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
}

.language-select:hover {
    border-color: var(--primary-600);
}

.language-select:focus {
    outline: none;
    border-color: var(--primary-600);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.compiler-workspace {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
}

.editor-panel,
.input-panel,
.output-panel {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.panel-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--gray-700);
    font-weight: 600;
}

.panel-header i {
    width: 20px;
    height: 20px;
    color: var(--primary-500);
}

.panel-actions {
    margin-left: auto;
    display: flex;
    gap: var(--spacing-sm);
}

.code-editor,
.input-area {
    width: 100%;
    min-height: 500px;
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    border: none;
    color: var(--text-primary);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
    line-height: 1.6;
    resize: vertical;
}

.code-editor:focus,
.input-area:focus {
    outline: none;
}

.io-panels {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.input-area {
    min-height: 200px;
}

.output-area {
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    min-height: 280px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
    overflow-x: auto;
}

.output-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--text-muted);
    text-align: center;
}

.output-placeholder i {
    width: 48px;
    height: 48px;
    margin-bottom: var(--spacing-md);
    opacity: 0.5;
}

.output-success {
    color: var(--success);
}

.output-error {
    color: var(--error);
}

.output-info {
    color: var(--primary-400);
}

/* ===================================
   Contests Section
   =================================== */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.filter-controls {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.filter-btn {
    padding: 0.5rem 1rem;
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
}

.filter-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.filter-btn.active {
    background: var(--primary-600);
    border-color: var(--primary-600);
    color: white;
}

.contests-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: var(--spacing-xl);
}

.contest-card {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    transition: all var(--transition-base);
    cursor: pointer;
}

.contest-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-600);
}

.contest-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: var(--spacing-md);
}

.contest-badge {
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-md);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
}

.badge-easy {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success);
}

.badge-medium {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning);
}

.badge-hard {
    background: rgba(239, 68, 68, 0.1);
    color: var(--error);
}

.badge-ongoing {
    background: rgba(59, 130, 246, 0.1);
    color: var(--primary-400);
}

.badge-upcoming {
    background: rgba(139, 92, 246, 0.1);
    color: var(--accent-500);
}

.badge-completed {
    background: rgba(107, 114, 128, 0.1);
    color: var(--gray-400);
}

.contest-title {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
}

.contest-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    font-size: 0.95rem;
}

.contest-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--bg-tertiary);
}

.meta-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--text-muted);
    font-size: 0.875rem;
}

.meta-item i {
    width: 16px;
    height: 16px;
}

.contest-actions {
    display: flex;
    gap: var(--spacing-sm);
}

/* ===================================
   Create Contest Form
   =================================== */
.create-contest-form {
    max-width: 900px;
    margin: 0 auto;
}

.form-card {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-2xl);
}

.form-section {
    margin-bottom: var(--spacing-2xl);
    padding-bottom: var(--spacing-2xl);
    border-bottom: 1px solid var(--bg-tertiary);
}

.form-section:last-of-type {
    border-bottom: none;
}

.form-section-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-lg);
    color: var(--primary-400);
}

.form-section-title i {
    width: 24px;
    height: 24px;
}

.form-group {
    margin-bottom: var(--spacing-lg);
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
    color: var(--text-primary);
}

.form-input,
.form-textarea,
.form-select {
    width: 100%;
    padding: 0.75rem 1rem;
    background: var(--bg-primary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: inherit;
    transition: all var(--transition-base);
}

.form-input:focus,
.form-textarea:focus,
.form-select:focus {
    outline: none;
    border-color: var(--primary-600);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.form-textarea {
    resize: vertical;
    font-family: inherit;
}

.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
}

.test-case-item {
    background: var(--bg-primary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

.form-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: flex-end;
    margin-top: var(--spacing-xl);
}

/* ===================================
   Leaderboard Section
   =================================== */
.leaderboard-card {
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.leaderboard-header {
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--bg-tertiary);
}

.leaderboard-tabs {
    display: flex;
    gap: var(--spacing-sm);
}

.tab-btn {
    padding: 0.5rem 1rem;
    background: none;
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
}

.tab-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.tab-btn.active {
    background: var(--primary-600);
    color: white;
}

.leaderboard-table {
    overflow-x: auto;
}

.leaderboard-table table {
    width: 100%;
    border-collapse: collapse;
}

.leaderboard-table th,
.leaderboard-table td {
    padding: var(--spacing-lg);
    text-align: left;
}

.leaderboard-table th {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    font-weight: 600;
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.leaderboard-table tbody tr {
    border-bottom: 1px solid var(--bg-tertiary);
    transition: all var(--transition-fast);
}

.leaderboard-table tbody tr:hover {
    background: var(--bg-tertiary);
}

.rank-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    font-weight: 700;
}

.rank-1 {
    background: linear-gradient(135deg, #ffd700, #ffed4e);
    color: #000;
}

.rank-2 {
    background: linear-gradient(135deg, #c0c0c0, #e8e8e8);
    color: #000;
}

.rank-3 {
    background: linear-gradient(135deg, #cd7f32, #e8a87c);
    color: #000;
}

.rank-other {
    background: var(--bg-tertiary);
    color: var(--text-secondary);
}

.user-info {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-600), var(--accent-600));
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    color: white;
}

.score-value {
    font-weight: 700;
    color: var(--primary-400);
    font-size: 1.125rem;
}

/* ===================================
   Toast Notification
   =================================== */
.toast {
    position: fixed;
    bottom: -100px;
    right: var(--spacing-xl);
    background: var(--bg-secondary);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    box-shadow: var(--shadow-xl);
    transition: all var(--transition-base);
    z-index: 2000;
    min-width: 300px;
}

.toast.show {
    bottom: var(--spacing-xl);
}

.toast-icon {
    width: 24px;
    height: 24px;
    color: var(--success);
}

.toast-message {
    color: var(--text-primary);
    font-weight: 500;
}

/* ===================================
   Loading Overlay
   =================================== */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(15, 23, 42, 0.9);
    backdrop-filter: blur(4px);
    display: none;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: var(--spacing-lg);
    z-index: 3000;
}

.loading-overlay.show {
    display: flex;
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--bg-tertiary);
    border-top-color: var(--primary-500);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

.loading-overlay p {
    color: var(--text-primary);
    font-weight: 600;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 1024px) {
    .compiler-workspace {
        grid-template-columns: 1fr;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 80px;
        left: 0;
        right: 0;
        background: var(--bg-secondary);
        border-bottom: 1px solid var(--bg-tertiary);
        flex-direction: column;
        padding: var(--spacing-lg);
        transform: translateY(-100%);
        opacity: 0;
        transition: all var(--transition-base);
        pointer-events: none;
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        pointer-events: all;
    }
    
    .nav-toggle {
        display: block;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-description {
        font-size: 1rem;
    }
    
    .hero-actions {
        flex-direction: column;
    }
    
    .features-grid,
    .contests-grid {
        grid-template-columns: 1fr;
    }
    
    .compiler-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .compiler-controls {
        flex-direction: column;
    }
    
    .section-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .form-actions {
        flex-direction: column;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    h3 { font-size: 1.5rem; }
    
    .hero-title {
        font-size: 1.75rem;
    }
    
    .stat-card {
        flex-direction: column;
        text-align: center;
    }
}

/* ===================================
   Print Styles
   =================================== */
@media print {
    .navbar,
    .nav-toggle,
    .toast,
    .loading-overlay {
        display: none !important;
    }
    
    .section {
        display: block !important;
        page-break-after: always;
    }
    
    body {
        background: white;
        color: black;
    }
}