/* ===================================
   CSS RESET & BASE STYLES
   =================================== */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    /* Color Palette - Modern & Professional */
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #10b981;
    --secondary-dark: #059669;

    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-light: #9ca3af;

    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;

    --border-color: #e5e7eb;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    --border-radius-lg: 16px;

    --shadow-sm: 0 1px 2px 0 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);

    --transition-fast: 150ms ease-in-out;
    --transition-normal: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;

    --max-width: 1200px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
}

html {
    scroll-behavior: smooth;
}

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

/* ===================================
   TYPOGRAPHY
   =================================== */
h1, h2, h3, h4, h5, h6 {
    line-height: 1.2;
    font-weight: 700;
    color: var(--text-primary);
}

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; }

p {
    margin-bottom: var(--spacing-sm);
}

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

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

/* ===================================
   LAYOUT UTILITIES
   =================================== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===================================
   HEADER
   =================================== */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-sm);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) 0;
}

.logo-link {
    text-decoration: none;
}

.logo {
    font-size: 1.75rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin: 0;
}

.nav-list {
    display: flex;
    list-style: none;
    gap: var(--spacing-md);
    align-items: center;
}

.nav-link {
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: all var(--transition-fast);
}

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

/* Mobile Menu Toggle Button */
.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    z-index: 101;
    position: relative;
}

.hamburger-icon {
    display: block;
    width: 28px;
    height: 2px;
    background: var(--text-primary);
    position: relative;
    transition: all var(--transition-normal);
}

.hamburger-icon::before,
.hamburger-icon::after {
    content: '';
    display: block;
    width: 28px;
    height: 2px;
    background: var(--text-primary);
    position: absolute;
    transition: all var(--transition-normal);
}

.hamburger-icon::before {
    top: -8px;
}

.hamburger-icon::after {
    top: 8px;
}

/* Hamburger Animation */
.mobile-menu-toggle.active .hamburger-icon {
    background: transparent;
}

.mobile-menu-toggle.active .hamburger-icon::before {
    top: 0;
    transform: rotate(45deg);
}

.mobile-menu-toggle.active .hamburger-icon::after {
    top: 0;
    transform: rotate(-45deg);
}

/* ===================================
   HERO SECTION
   =================================== */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: var(--spacing-2xl) 0;
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    color: white;
}

.hero-subtitle {
    font-size: 1.25rem;
    opacity: 0.95;
    line-height: 1.7;
    margin-bottom: 0;
}

/* ===================================
   FEATURES SECTION
   =================================== */
.features {
    padding: var(--spacing-2xl) 0;
    background: var(--bg-primary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

.feature-card {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    text-align: center;
    transition: all var(--transition-normal);
    border: 1px solid var(--border-color);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.feature-title {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.feature-description {
    color: var(--text-secondary);
    margin-bottom: 0;
}

/* ===================================
   GENERATOR SECTION
   =================================== */
.generator-section {
    padding: var(--spacing-2xl) 0;
    background: var(--bg-secondary);
}

.generator-wrapper {
    max-width: 900px;
    margin: 0 auto;
}

.qr-generator {
    background: var(--bg-primary);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-xl);
}

/* ===================================
   TABS
   =================================== */
.tabs {
    display: flex;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: var(--spacing-xs);
}

.tab {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    background: transparent;
    border: none;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
    position: relative;
}

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

.tab.active {
    color: var(--primary-color);
    background: var(--bg-tertiary);
}

.tab-icon {
    font-size: 1.2rem;
}

.tab-label {
    white-space: nowrap;
}

/* ===================================
   FORM ELEMENTS
   =================================== */
.form-container {
    margin-bottom: var(--spacing-lg);
}

.tab-panel {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

.tab-panel.active {
    display: block;
}

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

.input-group {
    margin-bottom: var(--spacing-md);
}

.input-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-md);
}

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

.input-field,
.textarea {
    width: 100%;
    padding: var(--spacing-sm);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    font-size: 1rem;
    font-family: inherit;
    transition: all var(--transition-fast);
    background: var(--bg-primary);
}

.input-field:focus,
.textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.input-help {
    display: block;
    margin-top: var(--spacing-xs);
    color: var(--text-light);
    font-size: 0.875rem;
}

.textarea {
    resize: vertical;
    min-height: 100px;
}

/* ===================================
   CUSTOMIZATION SECTION
   =================================== */
.customization-section {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    margin-bottom: var(--spacing-lg);
}

.section-title {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

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

@media (min-width: 872px) {
    .customization-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

.color-picker-group {
    display: flex;
    flex-direction: column;
    min-width: 0;
}

.color-input-wrapper {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
    min-width: 0;
}

.color-picker {
    width: 60px;
    min-width: 60px;
    height: 45px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    flex-shrink: 0;
}

.color-picker:hover {
    border-color: var(--primary-color);
}

.hex-input {
    flex: 1;
    min-width: 0;
    padding: var(--spacing-sm);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    font-family: 'Courier New', monospace;
    font-size: 0.95rem;
    transition: all var(--transition-fast);
}

.hex-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.size-control-group {
    display: flex;
    flex-direction: column;
    min-width: 0;
}

.size-slider {
    width: 100%;
    max-width: 100%;
    height: 8px;
    border-radius: 4px;
    background: var(--bg-tertiary);
    outline: none;
    -webkit-appearance: none;
}

.size-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.size-slider::-webkit-slider-thumb:hover {
    background: var(--primary-dark);
    transform: scale(1.1);
}

.size-slider::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    border: none;
    transition: all var(--transition-fast);
}

.size-slider::-moz-range-thumb:hover {
    background: var(--primary-dark);
    transform: scale(1.1);
}

/* ===================================
   BUTTONS
   =================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--border-radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    color: white;
    box-shadow: var(--shadow-md);
}

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

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--border-color);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.btn-large {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 1.125rem;
}

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

/* ===================================
   MESSAGES & ALERTS
   =================================== */
.error-message {
    display: none;
    padding: var(--spacing-md);
    background: #fee2e2;
    border: 1px solid #fca5a5;
    border-radius: var(--border-radius-sm);
    color: #991b1b;
    margin-bottom: var(--spacing-md);
}

.error-message.show {
    display: block;
    animation: slideDown 0.3s ease-out;
}

.success-message {
    display: none;
    padding: var(--spacing-sm);
    background: #d1fae5;
    border: 1px solid #6ee7b7;
    border-radius: var(--border-radius-sm);
    color: #065f46;
    margin-top: var(--spacing-md);
    text-align: center;
}

.success-message.show {
    display: block;
    animation: slideDown 0.3s ease-out;
}

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

/* ===================================
   LOADING STATE
   =================================== */
.loading {
    display: none;
    text-align: center;
    padding: var(--spacing-xl);
}

.loading.show {
    display: block;
}

.spinner {
    width: 50px;
    height: 50px;
    margin: 0 auto var(--spacing-md);
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

/* ===================================
   QR RESULT
   =================================== */
.qr-result {
    display: none;
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 2px solid var(--border-color);
    margin-top: var(--spacing-lg);
}

.qr-result.show {
    display: block;
    animation: fadeIn 0.5s ease-out;
}

.qr-image-container {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    margin: var(--spacing-lg) 0;
    display: inline-block;
}

.qr-image {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius-sm);
    box-shadow: var(--shadow-md);
}

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

/* ===================================
   HOW TO USE SECTION
   =================================== */
.how-to-use {
    padding: var(--spacing-2xl) 0;
    background: var(--bg-primary);
}

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

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

.step-card {
    text-align: center;
    padding: var(--spacing-lg);
}

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

.step-title {
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.step-description {
    color: var(--text-secondary);
    margin-bottom: 0;
}

/* ===================================
   USE CASES SECTION
   =================================== */
.use-cases {
    padding: var(--spacing-2xl) 0;
    background: var(--bg-secondary);
}

.use-cases-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.use-case-card {
    background: var(--bg-primary);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: all var(--transition-normal);
}

.use-case-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.use-case-title {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.use-case-description {
    color: var(--text-secondary);
    margin-bottom: 0;
}

/* ===================================
   FOOTER
   =================================== */
.footer {
    background: var(--text-primary);
    color: #e5e7eb;
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section {

}

.footer-title {
    font-size: 1.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-light), #a78bfa);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
}

.footer-description {
    color: #9ca3af;
    line-height: 1.7;
}

.footer-heading {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    color: white;
}

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

.footer-links li {
    margin-bottom: var(--spacing-xs);
}

.footer-link {
    color: #9ca3af;
    transition: color var(--transition-fast);
}

.footer-link:hover {
    color: var(--primary-light);
}

.footer-bottom {
    border-top: 1px solid #374151;
    padding-top: var(--spacing-lg);
    text-align: center;
}

.copyright {
    color: #9ca3af;
    margin-bottom: var(--spacing-xs);
}

.footer-note {
    color: #6b7280;
    font-size: 0.875rem;
    margin-bottom: 0;
}

/* ===================================
   RESPONSIVE DESIGN
   =================================== */
@media (max-width: 768px) {
    /* Show mobile menu toggle */
    .mobile-menu-toggle {
        display: block;
    }

    /* Remove header border on mobile to prevent double border */
    .header {
        border-bottom: none;
    }

    /* Hide navigation by default on mobile */
    .nav {
        position: fixed;
        top: 60px;
        left: 0;
        right: 0;
        background: #f3f4f6;
        border: none;
        box-shadow: var(--shadow-lg);
        max-height: 0;
        overflow: hidden;
        transition: max-height var(--transition-normal);
    }

    /* Show navigation when active */
    .nav.active {
        max-height: 300px;
    }

    .nav-list {
        flex-direction: column;
        gap: 0;
        padding: var(--spacing-md) 0;
    }

    .nav-list li {
        width: 100%;
    }

    .nav-link {
        display: block;
        width: 100%;
        padding: var(--spacing-md);
        text-align: center;
        border-radius: 0;
    }

    .nav-link:hover,
    .nav-link.active {
        background-color: #e5e7eb;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1.1rem;
    }

    .section-heading {
        font-size: 1.75rem;
    }

    .tabs {
        display: grid;
        grid-template-columns: repeat(4, minmax(120px, 1fr));
        grid-template-rows: repeat(2, 1fr);
        grid-auto-flow: column;
        gap: var(--spacing-xs);
        overflow-x: auto;
        overflow-y: hidden;
        -webkit-overflow-scrolling: touch;
    }

    .tab {
        justify-content: center;
        white-space: nowrap;
    }

    .input-row {
        grid-template-columns: 1fr;
    }

    .customization-grid {
        grid-template-columns: 1fr;
    }

    .action-buttons {
        flex-direction: column;
    }

    .action-buttons .btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: var(--spacing-xl) 0;
    }

    .hero-title {
        font-size: 1.75rem;
    }

    .qr-generator {
        padding: var(--spacing-md);
    }

    .features-grid,
    .steps-grid,
    .use-cases-grid {
        grid-template-columns: 1fr;
    }
}

/* ===================================
   ACCESSIBILITY
   =================================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Focus styles */
*:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 2px;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}