/* ===================================
   Modern Mobile-First Design System
   =================================== */

/* CSS Reset & Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  /* Color Palette - Modern & Vibrant */
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --accent-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
  --dark-gradient: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
  
  --bg-dark: #0f0f1e;
  --bg-card: rgba(255, 255, 255, 0.05);
  --bg-card-hover: rgba(255, 255, 255, 0.08);
  
  --text-primary: #ffffff;
  --text-secondary: rgba(255, 255, 255, 0.8);
  --text-muted: rgba(255, 255, 255, 0.6);
  
  --border-color: rgba(255, 255, 255, 0.1);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 20px rgba(102, 126, 234, 0.3);
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  
  /* Typography */
  --font-primary: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.5rem;
  
  /* Transitions */
  --transition-fast: 0.2s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  /* Border Radius */
  --radius-sm: 0.5rem;
  --radius-md: 1rem;
  --radius-lg: 1.5rem;
  --radius-xl: 2rem;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-primary);
  background: var(--bg-dark);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 100vh;
  position: relative;
}

/* ===================================
   Background Stars Animation
   =================================== */
.stars-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}

.stars {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 2px;
  height: 2px;
  border-radius: 50%;
  box-shadow: -447px 387px #c4c4c4, -401px 118px #fafafa, -109px 217px #d9d9d9, -680px -436px #e3e3e3, 514px 360px #cccccc, -708px 298px #e8e8e8, -696px -270px #ededed, 116px -128px #f7f7f7, 179px 35px white, -404px -90px whitesmoke, -331px -309px #c4c4c4, -363px -24px #d1d1d1, 277px 416px #fafafa, -145px -244px whitesmoke, 123px 62px #d4d4d4, -407px 418px #d9d9d9, 535px 237px #d9d9d9, -466px -78px #f7f7f7, 257px 287px #dedede, 327px -398px #e0e0e0, -602px -38px #c2c2c2, 128px 398px #e6e6e6, 274px -446px #d1d1d1, -602px -298px #c7c7c7, 526px -5px #c4c4c4, -90px -158px #fcfcfc, 5px 294px whitesmoke, -633px 229px #c4c4c4, -475px 427px #dedede, 586px -453px #f2f2f2, 180px -432px #c7c7c7, -637px -88px #cfcfcf, -453px 308px #d6d6d6, -111px 1px #d9d9d9, 573px -450px #ededed, 198px 300px #d6d6d6, -355px 166px #dedede, -715px 13px #e3e3e3, 262px -104px #d1d1d1, 147px 325px #dbdbdb, 1px 399px #dbdbdb, 286px -100px white, 43px -329px #e8e8e8, 617px 55px #d9d9d9, -168px -392px #cccccc, 84px 219px #c9c9c9, 507px -226px #d9d9d9, -327px -70px #e6e6e6, 386px -212px #c4c4c4, -717px 4px #cfcfcf, 502px -231px #e3e3e3, 302px 56px #ededed, 649px 341px #c7c7c7, 569px 350px #c9c9c9, 516px -31px #e6e6e6, 689px 447px #c2c2c2, 591px -206px #fafafa, 422px -137px #e6e6e6, -510px -324px #cccccc, -649px 287px #c2c2c2, -194px -48px #f7f7f7, -279px -329px #d1d1d1, -406px 478px #dbdbdb, -735px -87px #c9c9c9, 30px -197px #dedede, -564px 233px #e6e6e6, -486px -324px #ededed, -54px -7px #ededed, -441px -194px #e3e3e3, -133px -95px #e0e0e0, -722px -73px #d6d6d6, 595px 423px #ededed, 568px -39px #ededed, 370px 377px #d1d1d1, -419px -102px #fcfcfc, -450px 109px #c4c4c4, -57px -119px #d1d1d1, -582px 150px #e6e6e6, 206px -263px #cfcfcf, 582px -461px #c9c9c9, -268px -141px #d9d9d9, -148px 291px #c7c7c7, 254px -179px #c9c9c9, 725px 424px #f0f0f0, 391px -150px #ebebeb, 89px -299px #d4d4d4, 170px 1px #c9c9c9, 243px 209px #c7c7c7, 27px 460px #c9c9c9, -465px -380px #d4d4d4, 530px -360px whitesmoke, -626px 53px #e0e0e0, 706px 218px #d9d9d9, 40px -82px #cccccc, -5px -212px #e6e6e6, -742px 33px #ebebeb, -714px 478px #e0e0e0, -585px -125px #cccccc, -216px 348px #cfcfcf, 601px 332px #ededed, 344px -88px #c4c4c4, 659px -22px #d1d1d1, -411px 188px #d6d6d6, -423px -206px #fcfcfc, -359px -136px #cfcfcf, 612px 406px whitesmoke, 725px 96px whitesmoke, 363px -446px white, -204px 325px #c9c9c9, 740px 176px #fafafa, -489px -352px white, -638px 64px #dbdbdb, 537px -65px #dbdbdb, 151px -32px #ebebeb, 681px 212px #fcfcfc, 604px -149px #e6e6e6, -542px -398px #c4c4c4, -707px 66px whitesmoke, -381px 258px #cfcfcf, -30px 332px #d6d6d6, 512px -381px #c9c9c9, 195px 288px #cccccc, -278px 479px #c7c7c7, 27px -208px #d6d6d6, -288px 15px white, -680px 248px #dedede, 433px 31px #c9c9c9, 150px -206px #d4d4d4, -79px 247px white, -594px 115px #e0e0e0, 99px 292px #e0e0e0, 673px -269px #dedede, -257px -64px #d1d1d1, 449px 81px #f2f2f2, 18px -99px #d1d1d1, -694px 415px #f7f7f7, 240px 264px #e0e0e0, 450px -172px white, 383px 7px #e8e8e8, 338px -73px #c9c9c9, 291px -19px #ebebeb, 659px 137px #d1d1d1, 602px -6px #fcfcfc, 554px 249px #ebebeb, 625px 356px #d9d9d9, 579px -183px #d6d6d6, -20px 250px white;
  animation: fly 15s linear infinite;
  transform-style: preserve-3d;
}

.stars:before,
.stars:after {
  content: "";
  position: absolute;
  width: inherit;
  height: inherit;
  box-shadow: inherit;
  border-radius: 50%;
}

.stars:before {
  transform: translateZ(-300px);
  opacity: 0.6;
}

.stars:after {
  transform: translateZ(-600px);
  opacity: 0.4;
}

@keyframes fly {
  from {
    transform: translateZ(0px);
  }
  to {
    transform: translateZ(200px);
  }
}

/* ===================================
   Mobile Menu Toggle
   =================================== */
.mobile-menu-toggle {
  position: fixed;
  top: var(--spacing-md);
  right: var(--spacing-md);
  z-index: 1001;
  width: 48px;
  height: 48px;
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-md);
}

.mobile-menu-toggle:hover {
  background: var(--bg-card-hover);
  transform: scale(1.05);
}

.mobile-menu-toggle span {
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition-base);
}

.mobile-menu-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(7px, 7px);
}

.mobile-menu-toggle.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(7px, -7px);
}

/* Hide on desktop */
@media (min-width: 768px) {
  .mobile-menu-toggle {
    display: none;
  }
}

/* ===================================
   Navigation
   =================================== */
.main-nav {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(15, 15, 30, 0.8);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-color);
  transform: translateY(-100%);
  transition: transform var(--transition-base);
}

.main-nav.active {
  transform: translateY(0);
}

.nav-container {
  display: flex;
  flex-direction: column;
  padding: var(--spacing-lg) var(--spacing-md);
  gap: var(--spacing-xs);
}

.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,
.nav-link.active {
  background: var(--bg-card);
  color: var(--text-primary);
  transform: translateX(8px);
}

.nav-icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

/* Desktop Navigation */
@media (min-width: 768px) {
  .main-nav {
    transform: translateY(0);
  }
  
  .nav-container {
    flex-direction: row;
    justify-content: center;
    padding: var(--spacing-md);
    gap: var(--spacing-sm);
  }
  
  .nav-link:hover,
  .nav-link.active {
    transform: translateY(-2px);
  }
}

/* ===================================
   Main Content
   =================================== */
.main-content {
  position: relative;
  z-index: 1;
  padding-top: 80px;
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

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

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

.hero-title {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--spacing-md);
  animation: fadeInUp 0.8s ease;
}

.hero-subtitle {
  font-size: var(--font-size-xl);
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xl);
  animation: fadeInUp 0.8s ease 0.2s backwards;
}

.hero-link {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--primary-gradient);
  color: white;
  text-decoration: none;
  border-radius: var(--radius-xl);
  font-weight: 600;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-glow);
  animation: fadeInUp 0.8s ease 0.4s backwards;
}

.hero-link:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 32px rgba(102, 126, 234, 0.5);
}

.hero-link svg {
  width: 20px;
  height: 20px;
  transition: transform var(--transition-base);
}

.hero-link:hover svg {
  transform: translateX(4px);
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===================================
   Section Headers
   =================================== */
.section-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.section-title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.section-divider {
  width: 60px;
  height: 4px;
  background: var(--primary-gradient);
  margin: 0 auto;
  border-radius: 2px;
}

/* ===================================
   About Section
   =================================== */
.about-section {
  padding: var(--spacing-xl) 0;
}

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

.about-card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  transition: all var(--transition-base);
}

.about-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.about-info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.info-item {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
  padding: var(--spacing-md);
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-md);
  border-left: 3px solid transparent;
  background-image: linear-gradient(rgba(255, 255, 255, 0.03), rgba(255, 255, 255, 0.03)), var(--primary-gradient);
  background-origin: border-box;
  background-clip: padding-box, border-box;
}

.info-label {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  font-weight: 500;
}

.info-value {
  font-size: var(--font-size-lg);
  color: var(--text-primary);
  font-weight: 600;
}

/* QR Code Cards */
.qr-card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-base);
}

.qr-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.qr-wrapper {
  text-align: center;
}

.qr-image {
  width: 100%;
  max-width: 280px;
  height: auto;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
  margin-bottom: var(--spacing-md);
}

.qr-label {
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  font-weight: 500;
}

@media (min-width: 768px) {
  .about-grid {
    grid-template-columns: 1fr 1fr;
  }
  
  .info-item {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
  }
}

/* ===================================
   Teaching Section
   =================================== */
.teaching-section {
  padding: var(--spacing-xl) 0;
}

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

.teaching-card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  transition: all var(--transition-base);
}

.teaching-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.teaching-title {
  font-size: var(--font-size-xl);
  font-weight: 700;
  margin-bottom: var(--spacing-md);
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.teaching-intro {
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
  line-height: 1.8;
}

.learning-steps {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.step-item {
  display: flex;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.step-item:hover {
  background: rgba(255, 255, 255, 0.05);
  transform: translateX(8px);
}

.step-icon {
  font-size: var(--font-size-3xl);
  flex-shrink: 0;
}

.step-content h4 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
}

.step-content p {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  line-height: 1.6;
}

@media (min-width: 768px) {
  .teaching-grid {
    grid-template-columns: 1fr 1fr;
  }
}

/* ===================================
   Tips Section
   =================================== */
.tips-section {
  padding: var(--spacing-xl) 0 var(--spacing-2xl);
}

.tips-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
}

.tip-card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  text-align: center;
  transition: all var(--transition-base);
}

.tip-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(102, 126, 234, 0.3);
}

.tip-icon {
  font-size: var(--font-size-4xl);
  margin-bottom: var(--spacing-md);
}

.tip-card h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.tip-card p {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  line-height: 1.6;
}

.study-image {
  margin-top: var(--spacing-xl);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.study-image img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform var(--transition-slow);
}

.study-image:hover img {
  transform: scale(1.05);
}

@media (min-width: 640px) {
  .tips-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .tips-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* ===================================
   Music Player
   =================================== */
.music-player {
  position: fixed;
  bottom: var(--spacing-lg);
  right: var(--spacing-lg);
  z-index: 999;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-md);
}

.music-toggle {
  width: 56px;
  height: 56px;
  background: var(--primary-gradient);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-glow);
  transition: all var(--transition-base);
  z-index: 2;
}

.music-toggle:hover {
  transform: scale(1.1);
  box-shadow: 0 8px 32px rgba(102, 126, 234, 0.5);
}

.music-toggle svg {
  width: 24px;
  height: 24px;
  color: white;
}

.music-cover {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  object-fit: cover;
  box-shadow: var(--shadow-lg);
  animation: rotate 20s linear infinite;
  animation-play-state: paused;
  border: 3px solid rgba(255, 255, 255, 0.1);
}

@keyframes rotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

/* Mobile adjustments */
@media (max-width: 640px) {
  .music-player {
    bottom: var(--spacing-md);
    right: var(--spacing-md);
  }
  
  .music-toggle {
    width: 48px;
    height: 48px;
  }
  
  .music-toggle svg {
    width: 20px;
    height: 20px;
  }
  
  .music-cover {
    width: 80px;
    height: 80px;
  }
}

/* ===================================
   Footer
   =================================== */
.main-footer {
  position: relative;
  z-index: 1;
  background: rgba(15, 15, 30, 0.8);
  backdrop-filter: blur(20px);
  border-top: 1px solid var(--border-color);
  padding: var(--spacing-xl) 0;
  margin-top: var(--spacing-2xl);
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  text-align: center;
}

.footer-content p {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  margin-bottom: var(--spacing-xs);
}

.footer-content a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-base);
}

.footer-content a:hover {
  color: var(--text-primary);
  text-decoration: underline;
}

/* ===================================
   Responsive Typography
   =================================== */
@media (min-width: 768px) {
  :root {
    --font-size-3xl: 2.5rem;
    --font-size-4xl: 3rem;
  }
  
  .hero-title {
    font-size: var(--font-size-4xl);
  }
}

@media (min-width: 1024px) {
  :root {
    --font-size-3xl: 3rem;
    --font-size-4xl: 3.5rem;
  }
}

/* ===================================
   Utility Classes
   =================================== */
.text-gradient {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

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

/* Print styles */
@media print {
  .stars-container,
  .mobile-menu-toggle,
  .main-nav,
  .music-player {
    display: none !important;
  }
  
  body {
    background: white;
    color: black;
  }
}