/* ============================================
   钢结构技术服务平台 - 主样式文件
   ============================================ */

/* CSS Variables */
:root {
    /* Colors */
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary-color: #64748b;
    --success-color: #22c55e;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --info-color: #06b6d4;
    
    /* Text Colors */
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --text-light: #f8fafc;
    
    /* Background Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-dark: #0f172a;
    --bg-darker: #020617;
    
    /* Border Colors */
    --border-color: #e2e8f0;
    --border-light: #f1f5f9;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition: 300ms ease;
    --transition-slow: 500ms ease;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;
    
    /* Font */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    
    /* Container */
    --container-width: 1300px;
    --container-padding: 1.5rem;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--primary-dark);
}

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

ul, ol {
    list-style: none;
}

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

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

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

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    font-size: 0.9375rem;
    font-weight: 500;
    line-height: 1.5;
    border-radius: var(--radius);
    transition: all var(--transition-fast);
    cursor: pointer;
    border: 2px solid transparent;
}

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

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

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

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

.btn-outline-light {
    background-color: transparent;
    color: white;
    border-color: white;
}

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

.btn-lg {
    padding: 0.875rem 1.75rem;
    font-size: 1rem;
}

.btn-block {
    width: 100%;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* ============================================
   Header & Navigation
   ============================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: transparent;
    transition: all var(--transition);
}

.header.scrolled {
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-md);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.25rem;
    font-weight: 700;
    color: white;
    transition: color var(--transition-fast);
}

.header.scrolled .logo {
    color: var(--text-primary);
}

.logo-img {
    height: 48px;
    width: auto;
    object-fit: contain;
}

.nav-menu {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.nav-link {
    font-size: 0.9375rem;
    font-weight: 500;
    color: rgba(255, 255, 255, 0.9);
    transition: color var(--transition-fast);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: width var(--transition-fast);
}

.nav-link:hover,
.nav-link.active {
    color: white;
}

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.header.scrolled .nav-link {
    color: var(--text-secondary);
}

.header.scrolled .nav-link:hover,
.header.scrolled .nav-link.active {
    color: var(--primary-color);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

/* Language Switch */
.lang-switch {
    position: relative;
}

.lang-btn {
    display: flex;
    align-items: center;
    gap: 0.375rem;
    padding: 0.5rem 0.75rem;
    font-size: 0.875rem;
    color: white;
    border-radius: var(--radius);
    transition: all var(--transition-fast);
}

.header.scrolled .lang-btn {
    color: var(--text-secondary);
}

.lang-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.header.scrolled .lang-btn:hover {
    background-color: var(--bg-secondary);
}

.lang-dropdown {
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: 0.5rem;
    background-color: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-fast);
}

.lang-dropdown.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.lang-option {
    display: block;
    padding: 0.625rem 1rem;
    font-size: 0.875rem;
    color: var(--text-primary);
    white-space: nowrap;
}

.lang-option:hover {
    background-color: var(--bg-secondary);
    color: var(--primary-color);
}

/* Auth Buttons */
.auth-buttons {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.auth-buttons .btn-outline {
    color: white;
    border-color: rgba(255, 255, 255, 0.5);
}

.auth-buttons .btn-outline:hover {
    background-color: white;
    color: var(--primary-color);
    border-color: white;
}

.header.scrolled .auth-buttons .btn-outline {
    color: var(--primary-color);
    border-color: var(--primary-color);
}

.header.scrolled .auth-buttons .btn-outline:hover {
    background-color: var(--primary-color);
    color: white;
}

/* User Menu */
.user-menu {
    position: relative;
}

.user-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.375rem 0.75rem;
    border-radius: var(--radius-full);
    color: white;
    transition: all var(--transition-fast);
}

.header.scrolled .user-btn {
    color: var(--text-primary);
}

.user-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.header.scrolled .user-btn:hover {
    background-color: var(--bg-secondary);
}

.user-avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    object-fit: cover;
}

.user-name {
    font-size: 0.875rem;
    font-weight: 500;
}

.user-dropdown {
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: 0.5rem;
    min-width: 220px;
    background-color: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-fast);
}

.user-menu:hover .user-dropdown {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.user-info {
    padding: 1rem;
    background-color: var(--bg-secondary);
}

.user-email {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
}

.user-role {
    display: block;
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 0.25rem;
}

.dropdown-divider {
    height: 1px;
    background-color: var(--border-color);
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.dropdown-item:hover {
    background-color: var(--bg-secondary);
    color: var(--primary-color);
}

.dropdown-item i {
    width: 18px;
    text-align: center;
}

/* Mobile Menu Button */
.mobile-menu-btn {
    display: none;
    padding: 0.5rem;
    font-size: 1.25rem;
    color: white;
}

.header.scrolled .mobile-menu-btn {
    color: var(--text-primary);
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 80px;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, #1e3a5f 0%, #0f172a 50%, #1e293b 100%);
    z-index: -1;
}

.hero-bg::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><defs><pattern id="grid" width="10" height="10" patternUnits="userSpaceOnUse"><path d="M 10 0 L 0 0 0 10" fill="none" stroke="rgba(255,255,255,0.03)" stroke-width="0.5"/></pattern></defs><rect width="100" height="100" fill="url(%23grid)"/></svg>');
    opacity: 0.5;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(circle at 30% 50%, rgba(37, 99, 235, 0.15) 0%, transparent 50%);
}

.hero .container {
    position: relative;
    z-index: 1;
}

.hero-content {
    max-width: 700px;
    text-align: left;
    margin-bottom: 4rem;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    color: white;
    line-height: 1.2;
    margin-bottom: 1.5rem;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: 2rem;
    max-width: 500px;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.hero-stats {
    display: flex;
    gap: 4rem;
    padding: 2rem 0;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.stat-item {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    color: white;
}

.stat-label {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.6);
}

.scroll-indicator {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    animation: bounce 2s infinite;
}

.scroll-indicator a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    color: rgba(255, 255, 255, 0.5);
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.scroll-indicator a:hover {
    color: white;
    border-color: white;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateX(-50%) translateY(0);
    }
    40% {
        transform: translateX(-50%) translateY(-10px);
    }
    60% {
        transform: translateX(-50%) translateY(-5px);
    }
}

/* ============================================
   Section Styles
   ============================================ */
section {
    padding: 6rem 0;
}

.section-header {
    text-align: center;
    margin-bottom: 3rem;
}

.section-tag {
    display: inline-block;
    padding: 0.375rem 1rem;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--primary-color);
    background-color: rgba(37, 99, 235, 0.1);
    border-radius: var(--radius-full);
    margin-bottom: 1rem;
}

.section-title {
    font-size: 2.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.section-desc {
    font-size: 1.0625rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ============================================
   Services Section
   ============================================ */
.services {
    background-color: var(--bg-secondary);
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1.5rem;
}

.service-card {
    background-color: white;
    padding: 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    transition: all var(--transition);
}

.service-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.service-icon {
    width: 64px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border-radius: var(--radius);
    margin-bottom: 1.5rem;
}

.service-icon i {
    font-size: 1.5rem;
    color: white;
}

.service-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.service-desc {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.service-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--primary-color);
}

.service-link i {
    transition: transform var(--transition-fast);
}

.service-link:hover i {
    transform: translateX(4px);
}

/* ============================================
   About Section
   ============================================ */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.about-content .section-tag {
    margin-bottom: 0.75rem;
}

.about-content .section-title {
    text-align: left;
    margin-bottom: 1.5rem;
}

.about-text {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.7;
}

.about-features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin: 2rem 0;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--text-primary);
}

.feature-item i {
    color: var(--success-color);
}

.about-image {
    position: relative;
}

.about-image img {
    width: 100%;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
}

.experience-badge {
    position: absolute;
    bottom: -20px;
    left: -20px;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow-lg);
}

.exp-number {
    display: block;
    font-size: 2rem;
    font-weight: 700;
}

.exp-text {
    font-size: 0.875rem;
    opacity: 0.9;
}

/* ============================================
   Problem & Solution Sections
   ============================================ */
.problem-section,
.solution-section {
    padding: 4rem 0;
    text-align: center;
}

.problem-section {
    background: var(--bg-white);
}

.solution-section {
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
}

.problem-section .section-header,
.solution-section .section-header {
    max-width: 1100px;
    margin: 0 auto;
}

/* ============================================
   How It Works Section
   ============================================ */
.how-it-works {
    padding: 5rem 0;
    background: var(--bg-white);
}

.steps-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 3rem;
    margin-bottom: 4rem;
}

.step-card {
    text-align: center;
    padding: 2rem;
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: all var(--transition);
}

.step-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.step-number {
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    font-size: 1.5rem;
    font-weight: 700;
    border-radius: 50%;
    margin: 0 auto 1.5rem;
}

.step-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.step-card p {
    font-size: 1rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.cta-band {
    background: linear-gradient(135deg, #1e3a5f 0%, #0f172a 100%);
    border-radius: var(--radius-lg);
    padding: 3rem;
    text-align: center;
    color: white;
}

.cta-band h3 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: white;
}

.cta-band p {
    font-size: 1.125rem;
    margin-bottom: 2rem;
    color: rgba(255, 255, 255, 0.9);
}

/* ============================================
   Advantages Section (Removed)
   ============================================ */
/* .advantages {
    background: linear-gradient(135deg, #1e3a5f 0%, #0f172a 100%);
    color: white;
}

.advantages .section-tag {
    background-color: rgba(255, 255, 255, 0.1);
    color: white;
}

.advantages .section-title {
    color: white;
}

.advantages-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 2rem;
}

.advantage-card {
    text-align: center;
    padding: 2rem;
}

.advantage-icon {
    width: 80px;
    height: 80px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    margin: 0 auto 1.5rem;
    transition: all var(--transition);
}

.advantage-card:hover .advantage-icon {
    background-color: var(--primary-color);
    transform: scale(1.1);
}

.advantage-icon i {
    font-size: 2rem;
    color: white;
}

.advantage-card h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.advantage-card p {
    font-size: 0.9375rem;
    color: rgba(255, 255, 255, 0.7);
    line-height: 1.6;
} */

/* ============================================
   Contact Section
   ============================================ */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
}

.contact-info .section-tag {
    margin-bottom: 0.75rem;
}

.contact-info .section-title {
    text-align: left;
    margin-bottom: 1rem;
}

.contact-desc {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.7;
}

.contact-details {
    margin-bottom: 2rem;
}

.contact-item {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.contact-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: rgba(37, 99, 235, 0.1);
    border-radius: var(--radius);
    flex-shrink: 0;
}

.contact-icon i {
    font-size: 1.25rem;
    color: var(--primary-color);
}

.contact-text h4 {
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.contact-text p {
    font-size: 0.9375rem;
    color: var(--text-secondary);
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-link {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--bg-secondary);
    border-radius: 50%;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.social-link:hover {
    background-color: var(--primary-color);
    color: white;
}

/* Contact Form */
.contact-form-wrapper {
    background-color: white;
    padding: 2.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
}

.contact-form .form-group {
    margin-bottom: 1.5rem;
}

.contact-form label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.contact-form input,
.contact-form textarea {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 0.9375rem;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    transition: all var(--transition-fast);
}

.contact-form input:focus,
.contact-form textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

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

/* ============================================
   Footer
   ============================================ */
.footer {
    background-color: var(--bg-dark);
    color: white;
    padding: 4rem 0 2rem;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 3rem;
    padding-bottom: 3rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.25rem;
    font-weight: 700;
    color: white;
    margin-bottom: 1rem;
}

.footer-logo i {
    color: var(--primary-color);
}

.footer-desc {
    font-size: 0.9375rem;
    color: rgba(255, 255, 255, 0.6);
    line-height: 1.7;
}

.footer-links h4,
.footer-contact h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}

.footer-links ul li {
    margin-bottom: 0.75rem;
}

.footer-links a {
    font-size: 0.9375rem;
    color: rgba(255, 255, 255, 0.6);
    transition: color var(--transition-fast);
}

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

.footer-contact p {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.9375rem;
    color: rgba(255, 255, 255, 0.6);
    margin-bottom: 0.75rem;
}

.footer-contact i {
    width: 18px;
    color: var(--primary-color);
}

.footer-bottom {
    padding-top: 2rem;
    text-align: center;
}

.footer-bottom p {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.5);
}

/* ============================================
   Back to Top Button
   ============================================ */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition);
    z-index: 999;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background-color: var(--primary-dark);
    transform: translateY(-4px);
}

/* ============================================
   Toast Notifications
   ============================================ */
.toast-container {
    position: fixed;
    top: 1.5rem;
    right: 1.5rem;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.toast {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    min-width: 300px;
    max-width: 400px;
    padding: 1rem 1.25rem;
    background-color: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow-xl);
    animation: slideIn 0.3s ease;
}

.toast.success {
    border-left: 4px solid var(--success-color);
}

.toast.error {
    border-left: 4px solid var(--danger-color);
}

.toast.warning {
    border-left: 4px solid var(--warning-color);
}

.toast.info {
    border-left: 4px solid var(--info-color);
}

.toast-icon {
    font-size: 1.25rem;
}

.toast.success .toast-icon {
    color: var(--success-color);
}

.toast.error .toast-icon {
    color: var(--danger-color);
}

.toast.warning .toast-icon {
    color: var(--warning-color);
}

.toast.info .toast-icon {
    color: var(--info-color);
}

.toast-message {
    flex: 1;
    font-size: 0.9375rem;
    color: var(--text-primary);
}

.toast-close {
    padding: 0.25rem;
    color: var(--text-muted);
    transition: color var(--transition-fast);
}

.toast-close:hover {
    color: var(--text-primary);
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1024px) {
    .services-grid,
    .steps-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: white;
        flex-direction: column;
        padding: 1rem;
        gap: 0;
        box-shadow: var(--shadow-lg);
    }
    
    .nav-menu.active {
        display: flex;
    }
    
    .nav-link {
        color: var(--text-primary);
        padding: 0.75rem 1rem;
        display: block;
    }
    
    .mobile-menu-btn {
        display: block;
    }
    
    .auth-buttons {
        display: none;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 1.5rem;
    }
    
    .about-grid,
    .contact-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    
    .services-grid,
    .steps-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    
    .experience-badge {
        position: static;
        margin-top: 1rem;
    }
    
    .cta-band {
        padding: 2rem 1.5rem;
    }
    
    .cta-band h3 {
        font-size: 1.5rem;
    }
    
    .cta-band p {
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .section-title {
        font-size: 1.75rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .hero-buttons .btn {
        width: 100%;
    }
}