/* ============================================================
   顶捷软件 - 企业展示网站
   Design System & Global Styles
   ============================================================ */

/* ===== 1. CSS Custom Properties (Design Tokens) ===== */
:root {
    /* --- Brand Colors --- */
    --color-primary: #6c5ce7;
    --color-primary-dark: #5a4bd1;
    --color-primary-light: #8b83f0;
    --color-accent: #00d4ff;
    --color-accent-dark: #00a8cc;

    /* --- Gradients --- */
    --gradient-primary: linear-gradient(135deg, #6c5ce7, #00d4ff);
    --gradient-hero: linear-gradient(180deg, #0a0a1a 0%, #0f0f2a 50%, #0a0a1a 100%);
    --gradient-card: linear-gradient(145deg, rgba(108, 92, 231, 0.08), rgba(0, 212, 255, 0.04));
    --gradient-glow: radial-gradient(circle at 50% 50%, rgba(108, 92, 231, 0.15), transparent 60%);
    --gradient-divider: linear-gradient(90deg, transparent, rgba(108, 92, 231, 0.5), transparent);

    /* --- Backgrounds --- */
    --bg-primary: #0a0a1a;
    --bg-secondary: #0f0f2a;
    --bg-card: #151538;
    --bg-card-hover: #1c1c48;
    --bg-elevated: #1e1e4a;
    --bg-glass: rgba(15, 15, 42, 0.8);

    /* --- Text Colors --- */
    --text-primary: #e8e8f0;
    --text-secondary: #b0b0c8;
    --text-muted: #7a7a9a;
    --text-accent: #00d4ff;

    /* --- Borders --- */
    --border-color: rgba(108, 92, 231, 0.2);
    --border-hover: rgba(108, 92, 231, 0.5);
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;
    --border-radius-xl: 20px;
    --border-radius-full: 9999px;

    /* --- Shadows --- */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.4);
    --shadow-glow: 0 0 30px rgba(108, 92, 231, 0.3);
    --shadow-glow-strong: 0 0 50px rgba(108, 92, 231, 0.5);

    /* --- Typography --- */
    --font-primary: 'PingFang SC', 'Microsoft YaHei', 'Hiragino Sans GB', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', 'Cascadia Code', 'Fira Code', 'Consolas', monospace;

    --fs-display: clamp(2.2rem, 5vw, 3.8rem);
    --fs-h1: clamp(1.8rem, 4vw, 2.8rem);
    --fs-h2: clamp(1.4rem, 3vw, 2rem);
    --fs-h3: clamp(1.1rem, 2vw, 1.4rem);
    --fs-body: 1rem;
    --fs-sm: 0.875rem;
    --fs-xs: 0.75rem;

    --fw-light: 300;
    --fw-regular: 400;
    --fw-medium: 500;
    --fw-semibold: 600;
    --fw-bold: 700;

    --lh-heading: 1.25;
    --lh-body: 1.7;

    /* --- Spacing --- */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;
    --space-5xl: 8rem;

    /* --- Layout --- */
    --max-width: 1200px;
    --header-height: 72px;

    /* --- Transitions --- */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
    --transition-spring: 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* ===== 2. CSS Reset / Base ===== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--header-height);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-primary);
    font-size: var(--fs-body);
    font-weight: var(--fw-regular);
    line-height: var(--lh-body);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
    min-height: 100vh;
}

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

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

ul, ol {
    list-style: none;
}

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

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

::selection {
    background: rgba(108, 92, 231, 0.4);
    color: #fff;
}

:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

/* ===== 3. Typography ===== */
h1, h2, h3, h4, h5, h6 {
    font-weight: var(--fw-bold);
    line-height: var(--lh-heading);
}

.text-gradient {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ===== 4. Layout Utilities ===== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

.section {
    padding: var(--space-5xl) 0;
    position: relative;
}

.section__header {
    text-align: center;
    max-width: 700px;
    margin: 0 auto var(--space-3xl);
}

.section__tag {
    display: inline-block;
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 0.15em;
    padding: var(--space-xs) var(--space-md);
    border: 1px solid rgba(0, 212, 255, 0.3);
    border-radius: var(--border-radius-full);
    margin-bottom: var(--space-md);
    background: rgba(0, 212, 255, 0.05);
}

.section__title {
    font-size: var(--fs-h1);
    margin-bottom: var(--space-md);
    color: var(--text-primary);
}

.section__desc {
    font-size: var(--fs-body);
    color: var(--text-secondary);
    line-height: var(--lh-body);
}

/* ===== 5. Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 0.75rem 1.75rem;
    font-size: var(--fs-sm);
    font-weight: var(--fw-semibold);
    border-radius: var(--border-radius-md);
    transition: all var(--transition-base);
    white-space: nowrap;
    position: relative;
    overflow: hidden;
}

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

.btn--primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow);
}

.btn--gradient {
    background: var(--gradient-primary);
    color: #fff;
    background-size: 100% 100%;
    transition: all var(--transition-base);
}

.btn--gradient:hover {
    background-size: 150% 150%;
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow-strong);
}

.btn--outline {
    border: 1.5px solid rgba(255, 255, 255, 0.3);
    color: var(--text-primary);
    background: transparent;
}

.btn--outline:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
    background: rgba(0, 212, 255, 0.08);
    transform: translateY(-2px);
}

/* ===== 6. Header / Navigation ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    height: var(--header-height);
    transition: all var(--transition-base);
    background: transparent;
}

.header--scrolled {
    background: var(--bg-glass);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

.header__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

.header__logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 1.25rem;
    font-weight: var(--fw-bold);
    z-index: 1001;
}

.header__logo-icon {
    color: #fff;
    font-weight: var(--fw-bold);
    font-size: 1.15rem;
    background: var(--gradient-primary);
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--border-radius-sm);
}

.header__nav-list {
    display: flex;
    gap: var(--space-xl);
}

.header__nav-link {
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    color: var(--text-secondary);
    position: relative;
    padding: var(--space-xs) 0;
    transition: color var(--transition-fast);
}

.header__nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-primary);
    border-radius: 1px;
    transform: scaleX(0);
    transition: transform var(--transition-base);
}

.header__nav-link:hover,
.header__nav-link.active {
    color: var(--text-primary);
}

.header__nav-link:hover::after,
.header__nav-link.active::after {
    transform: scaleX(1);
}

.header__cta {
    font-size: var(--fs-xs);
    padding: 0.5rem 1.25rem;
}

.header__hamburger {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 32px;
    height: 32px;
    z-index: 1001;
    padding: 4px;
}

.header__hamburger span {
    display: block;
    width: 100%;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: all var(--transition-base);
    transform-origin: center;
}

.header__hamburger.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.header__hamburger.active span:nth-child(2) {
    opacity: 0;
    transform: scaleX(0);
}

.header__hamburger.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ===== 7. Hero Section ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    background: var(--gradient-hero);
}

.hero__canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
}

.hero__overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(ellipse at 50% 0%, rgba(108, 92, 231, 0.15) 0%, transparent 50%),
                radial-gradient(ellipse at 80% 80%, rgba(0, 212, 255, 0.08) 0%, transparent 40%);
}

.hero__content {
    position: relative;
    z-index: 2;
    text-align: center;
    padding-top: var(--header-height);
}

.hero__tag {
    display: inline-block;
    font-size: var(--fs-sm);
    color: var(--color-accent);
    font-weight: var(--fw-medium);
    margin-bottom: var(--space-lg);
    padding: var(--space-xs) var(--space-md);
    border: 1px solid rgba(0, 212, 255, 0.25);
    border-radius: var(--border-radius-full);
    background: rgba(0, 212, 255, 0.05);
    animation: fadeInUp 0.8s ease both 0.1s;
}

.hero__title {
    font-size: var(--fs-display);
    font-weight: var(--fw-bold);
    line-height: 1.15;
    margin-bottom: var(--space-lg);
    animation: fadeInUp 0.8s ease both 0.25s;
}

.hero__subtitle {
    font-size: clamp(1rem, 1.5vw, 1.15rem);
    color: var(--text-secondary);
    line-height: 1.8;
    max-width: 600px;
    margin: 0 auto var(--space-2xl);
    animation: fadeInUp 0.8s ease both 0.4s;
}

.hero__actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease both 0.55s;
}

.hero__actions .btn {
    padding: 0.85rem 2.25rem;
    font-size: var(--fs-body);
}

.hero__scroll {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-sm);
    color: var(--text-muted);
    font-size: var(--fs-xs);
    animation: fadeInUp 0.8s ease both 0.8s, bounce 2s ease-in-out infinite;
    z-index: 2;
}

.hero__scroll-icon {
    width: 18px;
    height: 30px;
    border: 2px solid var(--text-muted);
    border-radius: var(--border-radius-full);
    position: relative;
}

.hero__scroll-icon::after {
    content: '';
    position: absolute;
    top: 6px;
    left: 50%;
    transform: translateX(-50%);
    width: 3px;
    height: 6px;
    background: var(--text-muted);
    border-radius: 3px;
    animation: scrollDot 1.5s ease-in-out infinite;
}

/* ===== 8. About Section ===== */
.about {
    background: var(--bg-primary);
}

.about__grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-3xl);
    align-items: start;
}

.about__content h3 {
    font-size: var(--fs-h2);
    margin-bottom: var(--space-md);
    color: var(--text-primary);
}

.about__content p {
    color: var(--text-secondary);
    margin-bottom: var(--space-md);
    line-height: var(--lh-body);
}

.about__industries {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
}

.about__industry-tag {
    display: inline-block;
    padding: 0.3rem 0.8rem;
    font-size: var(--fs-xs);
    font-weight: var(--fw-medium);
    color: var(--text-secondary);
    background: rgba(108, 92, 231, 0.08);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-full);
    transition: all var(--transition-fast);
}

.about__industry-tag:hover {
    color: var(--color-accent);
    border-color: var(--border-hover);
    background: rgba(0, 212, 255, 0.06);
}

.about__content .btn {
    margin-top: var(--space-lg);
}

/* Stats Grid */
.about__stats {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
}

.stat-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--space-xl);
    text-align: center;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.stat-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: opacity var(--transition-base);
}

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

.stat-card:hover::before {
    opacity: 1;
}

.stat-card__number {
    display: block;
    font-size: 2.5rem;
    font-weight: var(--fw-bold);
    color: var(--text-primary);
    line-height: 1;
    margin-bottom: var(--space-xs);
}

.stat-card__suffix {
    font-size: 1.5rem;
    font-weight: var(--fw-bold);
    color: var(--color-accent);
}

.stat-card__label {
    display: block;
    font-size: var(--fs-sm);
    color: var(--text-muted);
    margin-top: var(--space-sm);
}

.stat-card__number-row {
    display: flex;
    align-items: baseline;
    justify-content: center;
    gap: 2px;
}

/* ===== 9. Services Section ===== */
.services {
    background: var(--bg-secondary);
}

.services__grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.service-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--space-2xl) var(--space-xl);
    text-align: center;
    transition: all var(--transition-base);
    position: relative;
}

.service-card::after {
    content: '';
    position: absolute;
    inset: -1px;
    border-radius: var(--border-radius-lg);
    background: var(--gradient-primary);
    z-index: -1;
    opacity: 0;
    transition: opacity var(--transition-base);
}

.service-card:hover {
    transform: translateY(-8px);
    border-color: transparent;
}

.service-card:hover::after {
    opacity: 1;
}

.service-card__icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--space-lg);
    color: var(--color-accent);
    background: rgba(0, 212, 255, 0.08);
    border-radius: var(--border-radius-lg);
    padding: 12px;
    transition: all var(--transition-base);
}

.service-card:hover .service-card__icon {
    background: rgba(0, 212, 255, 0.15);
    box-shadow: 0 0 20px rgba(0, 212, 255, 0.2);
    transform: scale(1.1);
}

.service-card__title {
    font-size: var(--fs-h3);
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.service-card__desc {
    font-size: var(--fs-sm);
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ===== 10. Process Section ===== */
.process {
    background: var(--bg-primary);
}

.process__timeline {
    position: relative;
    max-width: 1000px;
    margin: 0 auto;
}

.process__line {
    display: none;
}

.process__steps {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl) var(--space-lg);
}

.process-step {
    text-align: center;
    position: relative;
}

.process-step__marker {
    margin-bottom: var(--space-md);
}

.process-step__marker span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--gradient-primary);
    color: #fff;
    font-size: var(--fs-sm);
    font-weight: var(--fw-bold);
    position: relative;
    z-index: 1;
}

.process-step__dot {
    display: none;
}

.process-step__card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--space-lg);
    transition: all var(--transition-base);
}

.process-step__card:hover {
    border-color: var(--border-hover);
    box-shadow: var(--shadow-glow);
    transform: translateY(-4px);
}

.process-step__card h3 {
    font-size: var(--fs-h3);
    margin-bottom: var(--space-xs);
    color: var(--text-primary);
}

.process-step__card p {
    font-size: var(--fs-sm);
    color: var(--text-secondary);
}

/* ===== 11. Contact Section ===== */
.contact {
    background: var(--bg-primary);
}

.contact__grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-3xl);
    max-width: 1000px;
    margin: 0 auto;
}

.contact__form {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--space-2xl);
}

.contact__form-note {
    font-size: var(--fs-xs);
    color: var(--text-muted);
    margin-top: var(--space-md);
    text-align: center;
}

.contact__submit {
    width: 100%;
    padding: 0.9rem;
    font-size: var(--fs-body);
    margin-top: var(--space-sm);
}

.contact__submit svg {
    transition: transform var(--transition-fast);
}

.contact__submit:hover svg {
    transform: translate(3px, -3px);
}

.contact__info {
    display: flex;
    flex-direction: column;
    gap: var(--space-2xl);
}

.contact__info-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: var(--space-2xl);
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.contact__info-item {
    display: flex;
    gap: var(--space-md);
    align-items: flex-start;
}

.contact__info-icon {
    flex-shrink: 0;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(0, 212, 255, 0.08);
    border-radius: var(--border-radius-md);
    color: var(--color-accent);
}

.contact__info-item h4 {
    font-size: var(--fs-sm);
    color: var(--text-primary);
    margin-bottom: 2px;
}

.contact__info-item p {
    font-size: var(--fs-sm);
    color: var(--text-secondary);
}

.contact__social h4 {
    font-size: var(--fs-sm);
    color: var(--text-primary);
    margin-bottom: var(--space-md);
}

.contact__social-links {
    display: flex;
    gap: var(--space-md);
}

.contact__social-link {
    width: 42px;
    height: 42px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-md);
    color: var(--text-muted);
    transition: all var(--transition-fast);
}

.contact__social-link:hover {
    color: var(--color-accent);
    border-color: var(--color-accent);
    background: rgba(0, 212, 255, 0.08);
    transform: translateY(-2px);
}

/* ===== 13. Form Elements ===== */
.form-group {
    margin-bottom: var(--space-md);
}

.form-group label {
    display: block;
    font-size: var(--fs-sm);
    font-weight: var(--fw-medium);
    color: var(--text-primary);
    margin-bottom: var(--space-xs);
}

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

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(108, 92, 231, 0.15);
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--text-muted);
}

.form-group input.error,
.form-group textarea.error {
    border-color: #ff4757;
    box-shadow: 0 0 0 3px rgba(255, 71, 87, 0.1);
}

.form-error-msg {
    font-size: var(--fs-xs);
    color: #ff4757;
    margin-top: var(--space-xs);
    display: none;
}

.form-error-msg.show {
    display: block;
}

/* ===== 14. Footer ===== */
.footer {
    background: #060618;
    border-top: 1px solid var(--border-color);
    padding: var(--space-3xl) 0 var(--space-lg);
}

.footer__grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: var(--space-2xl);
    margin-bottom: var(--space-2xl);
}

.footer__logo {
    font-size: 1.15rem;
    font-weight: var(--fw-bold);
    color: var(--text-primary);
    margin-bottom: var(--space-md);
    display: inline-block;
}

.footer__logo span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    color: #fff;
    font-weight: var(--fw-bold);
    font-size: 0.9rem;
    background: var(--gradient-primary);
    border-radius: var(--border-radius-sm);
    vertical-align: middle;
    margin-right: 2px;
}

.footer__brand p {
    font-size: var(--fs-sm);
    color: var(--text-muted);
    line-height: 1.7;
    max-width: 280px;
}

.footer__links h4 {
    font-size: var(--fs-sm);
    font-weight: var(--fw-semibold);
    color: var(--text-primary);
    margin-bottom: var(--space-md);
}

.footer__links ul {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.footer__links li,
.footer__links a {
    font-size: var(--fs-sm);
    color: var(--text-muted);
    transition: color var(--transition-fast);
}

.footer__links a:hover {
    color: var(--color-accent);
}

.footer__bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.06);
    padding-top: var(--space-lg);
    text-align: center;
    font-size: var(--fs-xs);
    color: var(--text-muted);
}

.footer__bottom a {
    color: var(--text-secondary);
}

.footer__bottom a:hover {
    color: var(--color-accent);
}

/* ===== 15. Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 999;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all var(--transition-base);
    cursor: pointer;
}

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

.back-to-top:hover {
    background: var(--color-primary);
    border-color: var(--color-primary);
    color: #fff;
    transform: translateY(-4px);
    box-shadow: var(--shadow-glow);
}

/* ===== 16. Animations & Keyframes ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateX(-50%) translateY(0);
    }
    40% {
        transform: translateX(-50%) translateY(-6px);
    }
    60% {
        transform: translateX(-50%) translateY(-3px);
    }
}

@keyframes scrollDot {
    0% {
        opacity: 1;
        top: 6px;
    }
    100% {
        opacity: 0;
        top: 18px;
    }
}

@keyframes pulse {
    0%, 100% {
        box-shadow: 0 0 0 0 rgba(108, 92, 231, 0.4);
    }
    50% {
        box-shadow: 0 0 0 12px rgba(108, 92, 231, 0);
    }
}

/* Scroll Reveal Animations */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.7s ease-out, transform 0.7s ease-out;
}

.reveal.revealed {
    opacity: 1;
    transform: translateY(0);
}

/* Stagger delays */
.reveal:nth-child(2) { transition-delay: 0.1s; }
.reveal:nth-child(3) { transition-delay: 0.2s; }
.reveal:nth-child(4) { transition-delay: 0.3s; }
.reveal:nth-child(5) { transition-delay: 0.4s; }
.reveal:nth-child(6) { transition-delay: 0.5s; }

/* Form feedback */
.form-success,
.form-error {
    display: none;
    text-align: center;
    padding: var(--space-md);
    border-radius: var(--border-radius-md);
    font-size: var(--fs-sm);
    margin-top: var(--space-md);
}

.form-success.show,
.form-error.show {
    display: block;
}

.form-success {
    background: rgba(0, 200, 100, 0.1);
    border: 1px solid rgba(0, 200, 100, 0.3);
    color: #00c864;
}

.form-error {
    background: rgba(255, 71, 87, 0.1);
    border: 1px solid rgba(255, 71, 87, 0.3);
    color: #ff4757;
}

/* ===== 17. Responsive Design ===== */

/* Tablet (max-width: 1024px) */
@media (max-width: 1024px) {
    :root {
        --space-5xl: 5rem;
    }

    .section {
        padding: var(--space-4xl) 0;
    }

    /* Hero */
    .hero__title {
        font-size: clamp(2rem, 6vw, 3rem);
    }

    /* About */
    .about__grid {
        grid-template-columns: 1fr;
        gap: var(--space-2xl);
    }

    .about__stats {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--space-md);
    }

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

    .stat-card__number {
        font-size: 2rem;
    }

    /* Services */
    .services__grid {
        grid-template-columns: repeat(2, 1fr);
    }

    /* Process */
    .process__steps {
        grid-template-columns: repeat(2, 1fr);
    }

    /* Contact */
    .contact__grid {
        grid-template-columns: 1fr;
        max-width: 600px;
    }

    /* Footer */
    .footer__grid {
        grid-template-columns: 1fr 1fr;
    }
}

/* Mobile (max-width: 768px) */
@media (max-width: 768px) {
    :root {
        --header-height: 60px;
        --space-5xl: 4rem;
        --space-4xl: 3.5rem;
    }

    .section {
        padding: var(--space-3xl) 0;
    }

    .container {
        padding: 0 var(--space-md);
    }

    /* Header */
    .header__nav {
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: var(--bg-primary);
        display: flex;
        align-items: center;
        justify-content: center;
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-base);
    }

    .header__nav.active {
        opacity: 1;
        visibility: visible;
    }

    .header__nav-list {
        flex-direction: column;
        align-items: center;
        gap: var(--space-xl);
    }

    .header__nav-link {
        font-size: 1.15rem;
    }

    .header__cta {
        display: none;
    }

    .header__hamburger {
        display: flex;
    }

    /* Hero */
    .hero__title {
        font-size: clamp(1.8rem, 8vw, 2.4rem);
    }

    .hero__subtitle {
        font-size: 0.95rem;
    }

    .hero__subtitle br {
        display: none;
    }

    .hero__actions {
        flex-direction: column;
        align-items: center;
    }

    .hero__actions .btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }

    /* About */
    .about__stats {
        grid-template-columns: repeat(2, 1fr);
    }

    .stat-card__number {
        font-size: 1.75rem;
    }

    /* Services */
    .services__grid {
        grid-template-columns: 1fr;
        max-width: 400px;
        margin: 0 auto;
    }

    /* Process */
    .process__steps {
        grid-template-columns: 1fr;
        max-width: 350px;
        margin: 0 auto;
    }

    /* Contact */
    .contact__form {
        padding: var(--space-lg);
    }

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

    /* Footer */
    .footer__grid {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .footer__brand p {
        margin: 0 auto;
    }

    .footer__links ul {
        align-items: center;
    }

    /* Back to top */
    .back-to-top {
        bottom: 1.25rem;
        right: 1.25rem;
        width: 40px;
        height: 40px;
    }
}

/* Large Desktop (min-width: 1400px) */
@media (min-width: 1400px) {
    .hero__title {
        font-size: 4.5rem;
    }
}