/* ========================================
   QuizMaster - Common Styles
   ======================================== */

/* CSS Variables */
:root {
    --primary: #6366F1;
    --primary-dark: #4F46E5;
    --primary-light: #818CF8;
    --secondary: #EC4899;
    --secondary-dark: #DB2777;
    --accent: #F472B6;
    --gradient-primary: linear-gradient(135deg, #6366F1 0%, #8B5CF6 100%);
    --gradient-secondary: linear-gradient(135deg, #EC4899 0%, #F472B6 100%);
    --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 100%);

    --dark: #1E293B;
    --gray-900: #0F172A;
    --gray-800: #1E293B;
    --gray-700: #334155;
    --gray-600: #475569;
    --gray-500: #64748B;
    --gray-400: #94A3B8;
    --gray-300: #CBD5E1;
    --gray-200: #E2E8F0;
    --gray-100: #F1F5F9;
    --gray-50: #F8FAFC;

    --white: #FFFFFF;
    --black: #000000;

    --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);

    --radius-sm: 0.25rem;
    --radius: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --radius-full: 9999px;

    --transition-fast: 150ms;
    --transition: 300ms;
    --transition-slow: 500ms;

    --container-max: 1280px;
    --container-padding: 1.5rem;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--gray-700);
    background-color: var(--gray-50);
    overflow-x: hidden;
}

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

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

ul {
    list-style: none;
}

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

input {
    font-family: inherit;
    border: none;
    outline: none;
}

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

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

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 0.9375rem;
    font-weight: 600;
    border-radius: var(--radius-full);
    transition: all var(--transition);
    cursor: pointer;
    white-space: nowrap;
}

.btn svg {
    width: 18px;
    height: 18px;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--white);
    box-shadow: 0 4px 14px 0 rgb(99 102 241 / 0.39);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgb(99 102 241 / 0.23);
}

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

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

.btn-large {
    padding: 1rem 2rem;
    font-size: 1rem;
}

.btn-large svg {
    width: 20px;
    height: 20px;
}

/* Site Header */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    transition: all var(--transition);
}

.site-header.scrolled {
    background: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-md);
}

.header-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0.75rem var(--container-padding);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo-link {
    display: flex;
    align-items: center;
}

.logo-img {
    height: 54px;
    width: auto;
    transition: transform var(--transition);
}

/* 移动端优化 - 缩小Logo尺寸 */
@media (max-width: 767px) {
    .logo-img {
        height: 40px;
    }

    .header-container {
        padding: 0.5rem var(--container-padding);
    }
}

.logo-link:hover .logo-img {
    transform: scale(1.05);
}

.main-nav {
    display: none;
}

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

.nav-link {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--gray-600);
    position: relative;
    padding: 0.5rem 0;
}

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

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

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

.mobile-menu-btn {
    display: flex;
    flex-direction: column;
    gap: 5px;
    padding: 8px;
}

.hamburger-line {
    width: 24px;
    height: 2px;
    background: var(--gray-700);
    border-radius: 2px;
    transition: all var(--transition);
}

.mobile-menu-btn.active .hamburger-line:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.mobile-menu-btn.active .hamburger-line:nth-child(2) {
    opacity: 0;
}

.mobile-menu-btn.active .hamburger-line:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* Mobile Navigation Menu - Dropdown from top-right */
@media (max-width: 767px) {
    .main-nav {
        position: fixed;
        top: 60px;
        right: 0;
        width: 200px;
        background: var(--white);
        border-radius: 0 0 0 12px;
        box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
        transform: translateY(-10px);
        opacity: 0;
        visibility: hidden;
        transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        z-index: 1001;
        overflow: hidden;
        display: block;
    }

    .main-nav.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    .nav-list {
        flex-direction: column;
        padding: 0.5rem 0;
    }

    .nav-list li {
        transform: translateX(10px);
        opacity: 0;
        transition: all 0.25s ease;
    }

    .main-nav.active .nav-list li {
        transform: translateX(0);
        opacity: 1;
    }

    .main-nav.active .nav-list li:nth-child(1) {
        transition-delay: 0.05s;
    }

    .main-nav.active .nav-list li:nth-child(2) {
        transition-delay: 0.1s;
    }

    .main-nav.active .nav-list li:nth-child(3) {
        transition-delay: 0.15s;
    }

    .nav-link {
        display: block;
        font-size: 0.9375rem;
        font-weight: 600;
        color: var(--gray-700);
        padding: 0.75rem 1.25rem;
        transition: all 0.2s ease;
        border-left: 3px solid transparent;
    }

    .nav-link:hover,
    .nav-link.active {
        color: var(--primary);
        background: rgba(99, 102, 241, 0.08);
        border-left-color: var(--primary);
    }

    .nav-link::after {
        display: none;
    }

    /* Hide close button for dropdown style */
    .mobile-menu-close {
        display: none !important;
    }

    /* Overlay background */
    .mobile-menu-overlay {
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: rgba(0, 0, 0, 0.3);
        opacity: 0;
        visibility: hidden;
        transition: all 0.3s ease;
        z-index: 1000;
    }

    .mobile-menu-overlay.active {
        opacity: 1;
        visibility: visible;
    }
}

/* Footer */
.site-footer {
    background: var(--gray-900);
    color: var(--gray-300);
    padding: 4rem 0 2rem;
    margin-top: 4rem;
}

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

.footer-main {
    display: grid;
    grid-template-columns: 1fr;
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-brand {
    max-width: 300px;
}

.footer-logo {
    height: 45px;
    width: auto;
    margin-bottom: 1rem;
    filter: brightness(0) invert(1);
}

.footer-tagline {
    font-size: 0.9375rem;
    color: var(--gray-400);
    line-height: 1.7;
}

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

.footer-column h4 {
    font-size: 0.875rem;
    font-weight: 700;
    color: var(--white);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.footer-column ul {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.footer-column a {
    font-size: 0.9375rem;
    color: var(--gray-400);
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    padding-top: 2rem;
    border-top: 1px solid var(--gray-800);
    text-align: center;
}

.footer-bottom p {
    font-size: 0.875rem;
    color: var(--gray-500);
    margin-bottom: 0.5rem;
}

/* Section Styles */
.section-title {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 1.5rem;
}

.section-title svg {
    width: 28px;
    height: 28px;
    color: var(--primary);
}

/* Responsive Breakpoints */
@media (min-width: 640px) {
    :root {
        --container-padding: 2rem;
    }

    .footer-main {
        grid-template-columns: 1fr 2fr;
    }

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

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

    .mobile-menu-btn {
        display: none;
    }

    .nav-list {
        gap: 2.5rem;
    }
}

@media (min-width: 1024px) {
    :root {
        --container-padding: 2.5rem;
    }

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

/* Utility Classes */
.text-center {
    text-align: center;
}

.mt-4 {
    margin-top: 1rem;
}

.mb-4 {
    margin-bottom: 1rem;
}

/* Animation Keyframes */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

.fade-in {
    animation: fadeIn 0.6s ease-out forwards;
}

/* ========================================
   Google AdSense Ad Placements
   ======================================== */

/* Ad Container Base Styles */
.ad-container {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 1.5rem auto;
    min-height: 90px;
    background: var(--gray-50);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.ad-container.horizontal {
    max-width: 728px;
    min-height: 90px;
}

.ad-container.square {
    max-width: 336px;
    min-height: 280px;
}

.ad-container.in-article {
    max-width: 100%;
    min-height: 120px;
    margin: 2rem 0;
}

.ad-container.in-feed {
    max-width: 100%;
    min-height: 100px;
    margin: 1.5rem 0;
}

.ad-container.mobile-inline {
    max-width: 100%;
    min-height: 100px;
    margin: 1rem 0;
}

/* Ad Placeholder Styles (for development) */
.ad-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    min-height: inherit;
    background: linear-gradient(135deg, var(--gray-100) 0%, var(--gray-50) 100%);
    border: 2px dashed var(--gray-300);
    border-radius: var(--radius-lg);
    color: var(--gray-400);
    font-size: 0.875rem;
    text-align: center;
    padding: 1rem;
}

.ad-placeholder svg {
    width: 24px;
    height: 24px;
    margin-bottom: 0.5rem;
    opacity: 0.5;
}

.ad-placeholder-text {
    font-weight: 500;
}

/* Desktop: Horizontal ads */
@media (min-width: 768px) {
    .ad-container.horizontal {
        min-height: 90px;
    }
}

/* Mobile: Stacked layout */
@media (max-width: 767px) {
    .ad-container.horizontal {
        max-width: 320px;
        min-height: 100px;
    }

    .ad-container.square {
        max-width: 300px;
        min-height: 250px;
    }
}

/* Responsive Ad Grid */
.ad-grid {
    display: grid;
    gap: 1rem;
    margin: 1.5rem 0;
}

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

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

@media (max-width: 767px) {
    .ad-grid.two-columns,
    .ad-grid.three-columns {
        grid-template-columns: 1fr;
    }
}

/* Inline Ad between content sections */
.ad-inline {
    margin: 2rem 0;
    padding: 1rem 0;
    border-top: 1px solid var(--gray-200);
    border-bottom: 1px solid var(--gray-200);
}

/* Sticky ad for mobile (bottom of screen) */
.ad-sticky-bottom {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 999;
    display: none;
    justify-content: center;
    background: var(--white);
    padding: 0.5rem;
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.1);
}

.ad-sticky-bottom.visible {
    display: flex;
}

.ad-sticky-bottom .ad-container {
    margin: 0;
    min-height: 50px;
    max-width: 320px;
    border-radius: var(--radius);
}

.ad-sticky-bottom .ad-placeholder {
    border-radius: var(--radius);
    font-size: 0.75rem;
}

/* Ad label */
.ad-label {
    display: block;
    text-align: center;
    font-size: 0.6875rem;
    color: var(--gray-400);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: 0.25rem;
}

/* Ad wrapper for proper spacing */
.ad-wrapper {
    margin: 2rem auto;
    text-align: center;
}